Since Polly Hill's pioneering work (1969) on the economics of households in a northern Nigerian town, devoted largely to the analysis of what she termed the among Hausa women, there has been a proliferation of related studies (e.g., Barkow 1972; Simmons 1975; Hill 1977; Longhurst 1982; Schildkrout 1983; Callaway 1987).(1) These and many other works show that a vast majority of married Hausa women from such cities as Kano, Katsina, and Zaria, and their rural environs, often earn a sizeable income from petty or large-scale trade, while participating in the Islamic institution of purdah, in which they must remain secluded in the house. As a result of this work, the hidden trade has been viewed as a Hausa, a Nigerian, or perhaps a West African women's institution (Schildkrout 1983:125) that serves the dual function of enhancing both their prestige and modesty and of providing them with some remuneration for their household labor. Inasmuch as the studies demonstrate the prevalence of the hidden trade among Hausa women, several questions about it warrant further attention. First, although there is general agreement among observers that the practice provides Muslim women with a measure of autonomy within the household, there is less said about whether it mainly serves ends, augmenting the Islamic obligatory contribution of husbands, or has sociocultural purposes, being reinvested primarily in the Islamic system of marriage. Second, while the prevalence and nature of the trade in Hausaland has become quite clear, comparatively little attention has been accorded to the region's groups or individuals who do not trade, in terms of the variables that may affect the broad patterns and individual choices. Finally, very little compatible information is available for non-Hausa women in northern Nigeria, who constitute a sizeable percentage of the region's women,(2) even in the cities that were studied. Indeed, there appears to be a general assumption in the literature that all Muslim northern Nigerian women, given the right incentives (e.g., economic) and conditions, would choose to become active traders. In short, further research and analysis is necessary on the hidden trade, beyond the available case studies of Hausa women, that would broaden the perspectives on the practice, or more comprehensively cover ethnically heterogeneous communities dominated either by Hausa or other Muslim ethnic groups. Moreover, in view of Nigeria's current crisis and the government's designation of women-in-development activities as one way of alleviating its peoples' hardships, it is timely to determine exactly how widespread the institution actually is, and whether this is an economic venture which can be enhanced by future development activities. With these questions in mind, the following is a comparative study of Muslim women's trade in northern Nigeria, based on a review of the available relevant literature and on my own research(3) in an ethnically heterogeneous northern Nigerian city, Yola, in which Hausa are numerically and economically significant, yet are outnumbered by the Fulbe and members of other ethnic groups. The analysis will first comparatively summarize the data on Hausaland, discussing the factors that condition the women's roles and their decision to trade and the variations that obtain within Hausaland. The intensive, comparative study of Yola women will show that due to relatively uniform regional historical trends, political and factors, and cultural tendencies, the hidden trade is indeed prevalent outside Hausaland. The Muslim women of Yola, having shared in the common northern Nigerian experience, now participate in and rely on the practice, although the custom has been adapted to conform to local conditions and traditions and therefore varies in many respects from that of Hausaland. We shall also attempt to explain why the dominant ethnic group of Yola, the Fulbe, have thus far been resisting full incorporation into this tradition, largely on what they term as cultural grounds, and we will assess the impact of these attitudes on Yola's informal trade and food industries and on its non-Fulbe societies in general. …