Dicyphus hesperus Knight has good potential as a biological control agent for greenhouse pests in greenhouse tomato crops. The spatial distribution of D. hesperus was studied and a sampling plan was developed to monitor this species in greenhouse-grown tomatoes. Adults and nymphs are distributed in a more aggregated pattern among plants than within plants. The strong, significant relationship between the mean population density and the proportion of occupied sample units (leaves or plants) makes it possible to use a binomial or presence-absence sampling approach. Presence-absence sampling is an efficient method for crop management purposes because less time is needed to process the samples compared with a method where all insects are counted. At high densities, considering a sample unit to be occupied only when there are more than a determined number of individuals reduces considerably the optimum sample size required.