In this paper we review the literature on the association between polygyny and women's health in sub-Saharan Africa. We argue that polygyny is an example of "co-operative conflict" within households, with likely implications for the vulnerability of polygynous women to illness, and for their access to treatment. We begin with a review of polygyny and then examine vulnerability to sexually transmitted infections (STIs, including HIV) and differential reproductive outcomes. Polygyny is associated with an accelerated transmission of STIs, both because it permits a multiplication of sexual partners and because it correlates with low rates of condom use, poor communication between spouses, and age and power imbalances among other factors. Female fertility is affected by the interplay between marital rank, household status, and cultural norms in polygynous marriages. Finally, we present areas which have received only cursory attention: mental health and a premature, "social" menopause. Although data are scarce, polygyny seems to be associated with higher levels of anxiety and depression, particularly around stressful life events. It is our hope that the examples reviewed here will help build a framework for mixed method quality research, which in turn can inform decision makers on more appropriate, context-dependent health policies.