There is a lay assumption that women's sexual desire varies substantially over time, whereas men's is stable. This assumption is mirrored in prominent theories of desire, which posit that women are more variable than men in the extent to which they desire sex, and that women's sexual desire is more contextually sensitive than men's. We tested this assumption across three longitudinal studies. Study 1 assessed desire at 3 time points spanning 13 years (Nobservations = 5562), and Studies 2 and 3 (Nobservations = 11,282) assessed desire moment-to-moment over 7 days. When desire was measured over years, women were more variable in their sexual desire than men (Study 1). However, we found a different pattern of results when desire was measured over the short term. In Studies 2 and 3, we found no significant differences in women's and men's desire variability. The extent to which desire varied as a function of affective states (e.g., happiness) and relationship-oriented states (e.g., partner closeness) was similar for women and men, with some exceptions; women's desire was more negatively associated with tiredness and anger in Study 2. These data qualify existing assumptions about sex differences in sexual desire variability.