Cropping intensity in the cotton-wheat areas of Pakistan's Punjab is well below its potential, and also significantly lower than in neighbouring areas of India's Punjab. Analysis of annual cropping intensity indicates that access to irrigation water is the major factor explaining differences in cropping intensity in a cross-section of farmers. Ownership of a tractor plays a lesser role in increasing cropping intensity, although official credit policy has emphasized tractorization over investments in tubewells. Analysis of season-specific cropping intensity also indicates that lack of appropriate varieties for double cropping also constrain cropping intensity. It is estimated that cropping intensity could be increased by at least 30% through policies directed at improving water supplies and by promoting research on earlier varieties of cotton, maize and oilseeds.