Urban agriculture may have a role to play in addressing urban food insecurity problems, which are bound to become increasingly important with the secular trend towards the urbanization of poverty and of population in developing regions. Our understanding of the importance, nature and food security implications of urban agriculture is however plagued by a lack of good quality, reliable data. While studies based on survey data do exist for several major cities, much of the evidence is still qualitative if not anecdotal. Using a recently created dataset bringing together comparable, nationally representative household survey data for 15 developing or transition countries, this paper analyzes in a comparative international perspective the importance of urban agriculture for the urban poor and food insecure. Some clear hints do come from our analysis. On the one hand, the potential for urban agriculture to play a substantial role in urban poverty and food insecurity reduction should not be overemphasised, as its share in income and overall agricultural production is often quite limited. On the other hand, though, its role should also not be too easily dismissed, particularly in much of Africa and in all those countries in which agriculture provides a substantial share of income for the urban poor, and for those groups of households to which it constitutes an important source of livelihoods. We also find fairly consistent evidence of a positive statistical association between engagement in urban agriculture and dietary adequacy indicators.