The objective of this report is to analyze the effects of smallholder commercialization on food crop input use and productivity in rural Kenya. The main research issues were: (1) To examine the determinants of smallholder fertilizer use on food crops, with a focus on the effects of household and regional agricultural commercialization; (2) To examine the determinants of food crop productivity, again with a focus on the effects of commercialization; and (3) To discuss the implications of the findings for policy and additional research necessary to improve the contribution of cash cropping to rural food productivity growth and food security. A main premise of the paper is that the effects of commercialization are not uniform and cannot be generalized. The effects are hypothesized to differ both according to differences in the institutional/contractual arrangements between firms and smallholders, management decisions, and the level of credit and extension support provided to smallholders by the various private and parastatal firms involved in promoting smallholder cash crops.