Background: Information on the prevalence of undernutrition in adults in developing countries is mainly restricted to data on women. Literature reporting on the occurrence of female deprivation in developing countries, in particular in South Asia, suggests that differences between undernutrition prevalence in adult men and adult women might occur, but systematic information on the subject is lacking. Aim: The study compares undernutrition prevalence rates, based on prevalence of low body mass index (BMI < 18.5), in adult men and adult women in developing countries. Regional comparison is made between the main developing regions: Sub-Saharan Africa, South/Southeast Asia and Latin America. Subjects and methods: The study uses data as reported in 75 samples from 31 countries (divided over the three developing regions), in which anthropometric information has been collected in adult men and women within one and the same community. Results: Results indicate that, in general, prevalence rates of undernutrition are rather similar in adult men and women. However, there are regional differences. In communities in Sub-Saharan Africa, prevalence of low BMI is, on average, a few percent higher in men than in women; in South/Southeast Asia the reverse is the case. In some communities differences in undernutrition prevalence between men and women are exceptionally large. Conclusions: It can be concluded that, in general, information on undernutrition prevalence in women can be considered a proxy for undernutrition prevalence in all adults, men and women together. However, the finding that in South/Southeast Asia women's nutritional status relative to men's nutritional status compares unfavourably with results from other developing regions, in particular Sub-Saharan Africa, provides some support for the concept of female deprivation in South/Southeast Asia. Where large differences between prevalence of low BMI in men and women occur, gender-specific policies aimed at reducing undernutrition should be considered.