The probabilities of observing interactional synchrony (i.e., the precise coordination of body movement boundaries between interactants) were determined for all combinations of 2 or more people in a single 6-person discussion group (3 males and 3 females) comprising friends and strangers. It was found, using the binomial test, that only 1 dyad out of 57 comparisons showed significantly more synchrony than expected by chance. The hypothesis predicting more synchrony between friends than between stranger pairings was not supported. Also, the expectation that at speaker-switching locations, synchrony would be greater between consecutive-speaker than between speaker-listener pairings was not confirmed. However, a latency effect was significant; more synchrony was observed at switching locations where the interval of silence between contributions by successive speakers was 0-.5 sec than when overlapping speech occurred. Even this result was equivocal, since the observed probabilities of synchrony at all switching locations were not significantly different from chance occurrence. Previous studies emphasizing the dependence of human communication on interactional synchrony are questioned. (40 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1978 American Psychological Association.