Studied 8 goldfish in a 7-stage experiment. The general pattern of asymptotic free-operant red-green discrimination reversal was the same whether the schedule of reinforcement for response to S+ was VI 1 min. or VI 2 min., whether 1 or 3 days of training per reversal were given, whether reversal occurred at the start of an experimental session or in midsession, and whether 1 or 2 stimuli were encountered in each session. Rate of response to S+ increased gradually from a low initial level, decreasing slightly in the intersession interval, while rate of response to S- decreased gradually from a high initial level, increasing slightly in the intersession interval. The pattern was also the same as that found in discrete-trial experiments with goldfish but different from that found both in free-operant and discrete-trial experiments with pigeons. Data are reported for control Ss treated like the experimental Ss in all respects except for the correlation between color and reinforcement. (PsycINFO Database Record (c) 2006 APA, all rights reserved)