High levels of food insecurity and human immunodeficiency virus (HIV) infection place most breastfeeding mothers in Kenya at high risk of malnutrition. We examined the role of selected socio-economic, demographic and health factors as determinants of nutritional status among HIV-infected and HIV-uninfected mothers in rural Kenya and further examined the interrelationship between maternal nutritional and child nutritional status within this population. A cross-sectional design was used to collect data from non-pregnant mothers with children ages 4-24 months in Kisumu District, Kenya. Over 80% of the mothers were breastfeeding at the time of the study. Mean maternal body mass index (BMI) (21.60 ± 3.15) and percent body fat (22.29 ± 4.86) values were lower than among lactating mothers in other Sub-Sahara African countries. Maternal HIV status was not significantly associated with any of the maternal nutritional indicators assessed in the study. Breastfeeding, recent severe illness and having multiple children below 2 years of age were negatively associated with maternal nutritional status, while higher maternal age, socio-economic status and household food security were each positively associated with maternal nutritional status. Significant positive association was reported between maternal weight, height, BMI, mid-upper arm circumference (MUAC), body fat and fat-free mass estimates, and children's height-for-age, weight-for-age, weight-for-height and MUAC-for-age z-score. This analysis identifies determinants of maternal nutritional status in rural Kenya and highlights the importance of interventions that address malnutrition in both HIV-infected and HIV-uninfected mothers in rural Kenya. Significant association between maternal and child nutritional status stresses the importance of addressing maternal and young child nutritional status as interrelated factors. [ABSTRACT FROM AUTHOR]