Detection of water and social play reinforcers by a place conditioning method based on instrumental conditioning was investigated in rats and compared to detection by conditioned place preference, a method currently used primarily to measure drug reinforcement. Operant place conditioning measures of reinforcement were choices between the reward and nonreward chambers during an apparatus exploration test and during a discrete-trials choice test and also, in some experiments, choices and latencies of chamber entry during training. Three of these four measures showed larger reinforcement effects than did the conditioned place preference measure of relative time spent in the reward chamber. By all reinforcement measures, conditioned place preference training was effective with water reinforcement but was ineffective with social reinforcement. Operant place conditioning was effective with both reinforcers by all measures.