A total of 104 carcases were selected on the market in three age groups and four mass classes representative of the six fat classes of the classification system for carcase evaluation. Four subcutaneous fat thickness measurements were taken on the intact carcass. Carcases were deboned and the composition was determined. Fat, moisture, ash and protein analyses were performed on all the deboned carcasses. Between, as well as within age groups, there was some variation of single fat measurements and of combinations of such measurements which included or excluded carcase mass when used as predictors of the variation that occurred in certain carcase characteristics. The fat measurement between the 3rd and 4th lumbar vertebrae, 25 mm from the midline, was the most accurate predictor of differences in carcase composition. When two or more measurements were used in combination with carcase mass, the accuracy of predicting carcase composition was higher than the use of a single fat measurement. The visual evaluation of carcase fatness was a more reliable predictor of carcase composition than a single fat measurement.