SYNOPSIS. Pair formation is a prerequisite for reproduction in California condors and exploring the process has been central to the captive breeding program for this endangered species. Observations show that once birds reach sexual maturity they can form pairs within a matter of months; even birds who have lost or been separated from their mates will successfully bond with others. However, some adults who are housed together show little indication of pairing. When such birds are placed with other potential mates they frequently successfully pair and produce young, suggesting that individual differences play a role in pair formation. We recommend that adults who have not bonded within two years be housed with different potential mates. Condors raised together may or may not form pair bonds upon reaching sexual maturity; unfamiliar condors introduced at four years of age or older will form pair bonds. In the four cases where pairings have been successful the male initiates more intrapair interactions with aggressive behavior than does the female. Unpaired condors housed in groups do show courtship and the most dominant birds, usually males, are the most active in giving wings-out/head-down displays. Displays may be directed to males or females and may signal dominance and/or interest. Displays may be followed by mounts and one female may crowd in front of the bird to whom a male is displaying, increasing the chances that she will receive the display and be mounted. Displaying and the response to displaying birds may be mechanisms which influence mate selection.