In this study, Weiss's (1973) theorizing about the sources of emotional and social loneliness is elaborated - with notions about the asymmetric gratifications derived from marriage, about the conflicting loyalties that result from remarriage, and about selection into marriage - in order to reach an understanding of gender differences in loneliness, both in and outside of marriage. First and subsequent marriages are considered, as well as marital disruptions and never marrying. The data (N = 3737) are from the 1992 Dutch survey on older adults' living arrangements and social networks (NESTOR-LSN). Marital-history differences emerge, not only for emotional loneliness, but also (and contrary to Weiss's theoretical conceptualizations) for social loneliness. The marital-history differences in emotional and social loneliness are greater among men than women. For men, the marriage bond appears not only to be more central to emotional well-being than is the case for women but also to play a pivotal role in their involvement with others. Marital history offers the best explanation for differences in emotional loneliness among men, but social embeddedness characteristics also account for differences in emotional loneliness among women. Apparently, whereas men are more likely to find an intimate attachment in marriage, women also find protection from emotional loneliness in other close ties. The marital-history differences in social loneliness are largely mediated by social embeddedness characteristics, partly in different ways for men and women. Involvement in activities outside the home serves as the context for sociability for men, whereas parenthood plays a more important role in women's social engagements.