This note describes the results of various analyses which were carried out to study relations between measurements indicative of the amount of fat and lean in the carcasses of bacon pigs and their weaning weights, rates of gain between weaning and slaughter, and the lengths of the carcasses. The data involved were taken from a series of experiments, the original purpose of which was to compare various feeding treatments used between weaning and slaughter (205 lb.). The interpretation of these analyses presents some difficulty because of the many ways in which variations in weaning weight, for example, may occur; such variations arise naturally (because of variations in genotype, mothering ability of the sow, etc.) or may be induced by changing methods of management (systems of feeding, housing conditions, etc.). Considerable caution should therefore be exercised in attempting to extend the relations discussed here to conditions outside their own context. The difficulties are emphasised by the variety of different results which other workers have reported on the effect of weaning weight on subsequent development (reviewed by Braude, 1964).