none Seven methods of estimating percentage parasitism using graphical estimates of host or parasitoid recruitment are presented. Biases affecting these percentage parasitism estimates arise from the effect of mortality on graphical estimates of numbers entering a stage. These biases result in underestimation of parasitism in some of the methods examined and overestimation in others. The methods and their biases are discussed and illustrated with reference to data from four generations of Pieris rapae (L.) parasitized by Cotesia glomerata (L.). The general impact of these biases are discussed with reference to situations where the methods might be applied.