An individual’s socioeconomic status is one of the most important determinants of health care utilization. Yet, income as an indicator of socio-economic status is often underreported in survey data. This problem is compounded in African countries due to the existence of a large informal sector and cultural practices. To overcome this situation, this paper constructs a five-scale index based on households’ assets. This alternate measure of one’s socio-economic status is included as an explanatory variable in a negative binomial regression that examines the determinants of overnight hospital stays in Nigeria. My analysis suggests overnight hospital stays tend to decrease in both monetary and asset-based measures of socioeconomic status; although income tends to overstate this effect. Since the poor are more likely to stay more nights in a hospital, this may be an indication that the poor generally delay visits to health care facilities due to the predominance of user fees in the Nigerian health care system. To reduce this trend, there is the need for an expanded and affordable primary health care system that takes into account the local socio-economic environment. Finally, the study finds that the severity of ill-health is the single most important determinant of overnight hospital stays.