Chromosome variation in bottlenose dolphins can be visualized by fluorescent R-banding techniques. In the dolphin, eleven chromosome pairs carry a sufficient range of heteromorphisms (or variants) to be used in the exclusion or verification of paternity in breeding colonies having more than one sale. In an active breeding colony of bottlenose dolphins maintained at Sea World, CA, paternal discrimination has been made between various combinations of potential sires for calves born from 1978 to 1984. Two of the males could be positively assigned as fathers of some of the calves based on differences in hemoglobin electrophoretic pattern. For a number of the calves, however, hemoglobins did not discriminate between the potential sires. A third male has been verified as the father of these calves by chromosomal analysis. The positive ascertainment of paternity in long-range breeding programs is essential in colony management for the avoidance of inbreeding and can also be of value in testing the association of behavioral dominance with reproductive success. Effective discriminatory techniques are now available for paternity testing programs in dolphins.