The performance of commercial pigs is often below that seen under good experimental conditions. At least some of this decrease in performance can be attributed to environmental stressors. Stressors in the physical environment have been modelled (e.g., Black et al., 1986) allowing predictions of performance under varying conditions to be made. However, the influence of social stressors, including group size (N), space allowance (SPA, m2/BW0.67), feeder space allowance (FSA, feeder spaces/pig), and mixing, on pig performance, although undeniable, is generally ignored in pig growth modelling. The aim here was to quantify the effects of the major social stressors on the performance of growing pigs. Genetic variation in the ability to cope, and the social stressor effects were integrated to produce a more general growth model.