Recent d1scuss10ns of food secunty issues for developing countries have drawn attention to shortterm fluctuations in effective demand, especially of low-income households, as a critical area for pohcy analysts Real income instab1hty is presumed to be particularly acute in the rnral areas, given fluctuating agncultural production and volatile international markets for primary commod1ttes. This paper provides a systematic exanunation of income vanabihty in food and export crop production) develops a framework of analysis, and uses 1t to mvestigate the instability of total agricultural crop mcome in the Phtlippines and how that mcome has been affected by the marked increase m the share of export crops m the total value of crop production over the post-war penod. Some pohcy implications of the empirical results are briefly considered.