Male and female encoding-decoding of spontaneous and enacted nonverbal affective behavior was evaluated using the Buck (1977) slide-viewing paradigm. The eliciting stimuli were carefully selected and evaluated to insure a comparable emotional impact on both sexes, and all subjects received the same decoding task. Consistent with previous research, females were superior decoders overall. Also as predicted, females were superior encoders, principally when reacting spontaneously to the slides. Given no evidence of differential affective arousal, this sex difference for spontaneous encoding is interpreted to reflect differences in male-female display rules. Contrary to several previous findings spontaneous and enacted encoding measures were not strongly related, especially for males, where display rules may modify their spontaneous and enacted expressive behavior in comparison to females. There was no consistent positive or negative relationship between dimensional or category measures of encoding-decoding for either sex. Future investigations should separately evaluate encoding-decoding phenomena for each sex, employing more precise methods to evaluate the specific nonverbal behaviors actually important to the encoding-decoding communication process.