Samples of cricket frogs were collected in South Dakota and Texas at intervals throughout the spring, summer and autumn and acclimated for 5-7 days at 5, 15 and 25° C. Routine metabolic rates were determined at 15° C for acclimated frogs from both localities. Sample of Texas frogs collected in early April, late April and December were determined at 25° C as well. There were no statistically significant differences between the means of samples acclimated at 5 and 15° C and determined at 15° C on any date for either the South Dakota or the Texas frogs. Except for Texas frogs acclimated at 25 and 5° C in November, no significant differences were found among the means of the three acclimation groups from either locality from October into December. From April through July, with the exception of the Texas samples of 31 May, the frogs from both localities which were acclimated at 25° C had metabolic rates which were consistently higher than and significantly different from frogs acclimated at either 5 or 15° C. When frogs which had been collected at different times of the year and acclimated at the same temperature were compared, significant seasonal effects were found in all series except the Texas frogs acclimated at 5° C. Several pronounced seasonally related patterns were found. Low metabolic peaks were found in the 5 and 15° C acclimated frogs in late May and early October in both Texas and South Dakota frogs. In the South Dakota frogs acclimated at 25° C, the metabolic rates were highest in April and early May. The rates dropped somewhat in late May and remained fairly uniform until early October. In later October and November the metabolic rates of the warm acclimated frogs from South Dakota reached the lowest levels of the year. In the Texas frogs acclimated at 25° C and determined at 15° C, rates were highest in early April, dropped off by early May and remained fairly uniform into November. There was an indication of a slight increase in the metabolic rates of the warm acclimated frogs in December. The metabolic rates of Texas and South Dakota frogs with the same acclimation history were compared at approximately the same time of year. In no case were there significant differences attributable to locality for frogs acclimated at either 5 and 15° C. For frogs acclimated at 25° C, the mean metabolic rates of the South Dakota frogs were consistently higher than those of seasonally comparable Texas frogs from April to October and showed statistically significant differences for the 29 April–7 May, July and October comparisons. For the Texas frogs, the presence of inverse acclimation shown in the April frogs at 15° C with the warm acclimated animals having higher metabolic rates than those acclimated at 5 or 15° C, is replaced by either a weak or no acclimation effect at 25° C. The results of this study suggest that the pattern of inverse compensation at 15° C reported for Acris in earlier papers persists throughout much of the spring and summer in both the South Dakota and the Texas populations. The data further demonstrate the tendency for the metabolic rates of warm acclimated frogs from South Dakota to be higher at determination temperatures of about 15° C than comparable rates in Texas frogs. The seasonally related differences in the metabolic rates and also the differences in the metabolic rates of frogs from the two localities are interpreted in terms of published data on body temperature environmental temperature relationships in Acris and with published climatological data. The data are considered to be consistent with the hypothesis of the role of metabolic patterns in the maintenance of metabolic stability in thermally instable environments.