This paper provides a detailed quantitative description and analysis of the courtship and reproductive actions of Trichogaster leeri. Principal objectives are to present a description which will be useful in future comparative (and phylogenetic) studies, to determine how well detailed quantitative analysis provides insights into motivational mechanisms in these fish, and to see how well such data can be interpreted in terms of conventional ethological theories. Five pairs of mature fish provided complete records of fifteen spawnings (referred to below as sequences) ranging in duration from 2.7 to 5.5 hours. Reproductive and courtship activities in captive T. leeri and other anabantoid fishes occur in bouts of varying length which may be categorized on the basis of behavioral components present. While most bouts contain behaviors involving both fish, some bouts occur in which one fish (usually the female) shows no visible response to the action of the other. Examination of the organization of these bouts in the spawning sequence, the nature of activities in the different types of bouts, and the relationships between completeness of the bout, sex of the fish initiating the bout, and duration of intervals between bouts provide information about some of the factors influencing courtship and spawning. Bouts that are initiated by females are much more likely to be successful (proceed to clasping or spawning) than those initiated by males. Although males initiated over half of the bouts, spawning occurred in 88 female-initiated bouts and in only 10 male-initiated bouts. Thus we suggest that while male overt activity is often prominent several days to weeks before and after spawning, it is actually less critical in determining the outcome of sexual bouts than are female activities. Highly motivated males had little success in stimulating refractory females to successful spawning, whereas the converse appeared commonplace. Data on duration of intervals between bouts shows that females generally remained away from the nest and male longer after more complete bouts than after less complete (and typically shorter) bouts. Thus it seems unlikely that sexual and agonistic interplay during the bouts stimulated the female directly (arousal function). Furthermore, male-initiated bouts were found to be more successful the greater the duration of the interval preceding his approach. Although part of this apparent refractoriness is undoubtedly attributable to muscle fatigue or a similar phenomenon, performance of more complex actions in the more complete bouts may have some kind of central satiating (or drive-reducing) function. In the next section, variations in the frequency and duration of female approach, male leading-to-the-nest, male lateral spread, male circling, female courtship butting, male clasp, swimming inhibition, male butting and biting, male chasing, female appeasement, and total bout durations are presented in tables as they occurred in the 15 different types of bouts. Possible causes for these variations are discussed and the use of bout statistics in evaluating motivation levels is examined. For example, detailed examination of data on male butting and biting and male chasing suggest that male aggression only bouts may actually represent a rather lower degree of absolute aggressiveness in males than that which occurs in many bouts that succeed to more complex levels. Female sexual signals or responses may enhance aggression as part of a general increase in excitement, or partial female responses may lead to thwarting and resultant increased aggression. Much data is presented to support the contention that male courtship only bouts are least associated with aggressive motivation and are a good indicator of sexual motivation in the male. Furthermore, we suggest that the frequency of these two types of bouts in a sequence may be a fairly accurate reflection (if such is actually possible) of the relative strengths of sexual vs. aggressive motivation in a given sequence, because these two bout types occur in the absence of any measurable female responses, thus eliminating that critical variable from the list of factors which might influence male behavior. Evidence also is cited to support the contentions that female flight tendency is lower in female-initiated bouts and that male aggressiveness tends to be slightly higher in many (if not most) male-initiated bouts than in female-initiated bouts. There is also an indication that the nature of actions occurring in bouts have less influence on the activities of males in subsequent bouts than on those of females. In the next section, data on 10 of 11 activities discussed above in terms of their appearance in all bouts of a certain type (across the 15 sequences) are presented as they occur in each sequence, regardless of the bout type in which they occurred. The sequences are ranked (Table 18) from those in which the males were judged most aggressive (measured by frequency of male butts and bites) to those judged least aggressive. Aggression analysis shows that another potential measure of aggressiveness, male chasing frequency and duration, shows no direct correlation wih butting frequency, except perhaps a slightly negative one. The reasons for this are discussed in detail. The choice of male butting rate as the most nearly accurate indicator of male aggressiveness is justified on the basis of its agreement with other parameters such as female appeasement duration and circling duration (previously and subsequently shown to be associated with several indicators of aggression). High-aggression sequences tend to be those in which female responsiveness (or sexual initiative) is minimal. If male aggressiveness is determined exclusively internally, it is likely that female self-protection butting would occur more commonly than it apparently does in such sequences. It seems probable, therefore, that female behaviors may markedly effect motivation...