This research examined the efficacy of MDMA, MDE and their enantiomers in producing conditioned place preference (CPP) in rats. Training doses were 1 ml of 5 mg/ml MDMA, 1 ml of 4 mg/ml amphetamine and 1 ml 5 mg/ml MDE. After baseline preference was established, rats underwent 7 days of conditioning. CPP was tested on the eighth day, with CPP measured as time spent in the drug-associated versus saline-associated compartment. The first study failed to find CPP in MDMA-treated rats, though CPP was formed in amphetamine-treated rats. Noting that rats in the first study were group-housed, the authors conducted a second study comparing CPP in group-housed rats with socially isolated rats (1 animal per cage), with isolation beginning 1, 2 or 3 weeks prior to CPP procedure. Though no significant CPP effect was found, this study did find a trend for preferring the MDMA-associated compartment in isolated rats only. The effect was significant in rats isolated for 1 and two weeks (highest CPP in 2-week isolates), but not significant in 3-week isolates. Hence in the third study, all subjects were isolated for 2 weeks prior to CPP conditioning. Rats were trained either with racemic MDMA, R-(-)-MDMA or S-(+)-MDMA; comparable groups of rats were given racemic MDE or one of its two enantiomers. CPP was maintained by racemic MDMA, R-(-)- and S(+)-MDMA. Neither racemic MDE nor its enantiomers maintained CPP, though there was a trend for preferring the drug-associated compartment. The authors refer to lower 5-HT in social isolates versus group-housed rats, but do not offer supportive evidence, such as examination of 5-HT levels in group-housed versus isolated rats. A stress response to social isolation is also reported, though it was not formally assessed. Study findings for CPP are contrasted with findings of greater activity for the S-(+)-isomer versus the R-(-)-isomer. Finding that social isolation increases the reward-value of MDMA emphasizes the importance of environment stress in mediating the rewarding properties of psychoactive drugs.