Friendships and other relationships are crucial to human fitness, yet such relationships often terminate acrimoniously. We explore the pattern of relationship conflict, and the processes of reconciliation that are used to repair them. In this sample, an individual fell out with one member of their extended network, on average, every 7.2 months. Conflict with very close family is surprisingly high; nonetheless, most conflicts involve unrelated individuals (friends, colleagues), suggesting that kin relationships are relatively more buffered against the stresses that trigger conflict (reflecting the “kinship premium”). Around 40% of conflicts remain unreconciled after a year. There were striking sex differences in the intimacy of the relationships involved in breakdown, and the precipitating causes, as well as whom participants reported falling out with. These patterns may reflect women’s preference for fewer, more intimate (and correspondingly more fragile) relationships. The functional origins of this gender difference are not well understood.