Menstrual synchrony was not found for 30 cohabiting lesbian couples (mean time living together, 35 months), for whom 3 months of menstrual data were collected prospectively. A combined analysis with two previous studies of lesbian couples (Trevathan, W, Burleson, NH, Gregory, L (1993) No evidence for menstrual synchrony in lesbian couples. Psychoneuroendocrinology 18, 425-431; Weller, A, Weller, L (1992) Menstrual synchrony in female couples. Psychoneuroendocrinology 17, 171-177) also failed to reveal synchrony. These data are considered together with a previous study of Bedouin couples which found only a moderate degree of synchrony (Weller, A, Weller, L (1997a) Menstrual synchrony under optimal conditions: Bedouin families. J Comp Psychol 111, 143-151). When women live together for an extensive period of time and have intensive social contact among them, the intensive contact may not be conducive to menstrual synchrony.