This paper investigates the factors which affect naming performance for two groups of aphasic subjects. The effects of word age-of-acquisition, operativity, frequency, familiarity, imageability, concreteness, length and the visual complexity of the stimulus picture were examined. In contrast to previous studies, we found remarkably small effects of word frequency on naming performance; these studies, we argue, have failed to control sufficiently for the effects of variables which intercorrelate with frequency. However, many patients were significantly affected by age-of-acquisition even when any effects of frequency and familiarity had been accounted for. Operativity, imageability and word length were also predictive of naming performance for some of the patients investigated, unlike visual complexity. The applicability of conclusions drawn from groups of aphasics is again thrown into doubt, as these two groups showed different patterns of predictor variables, and the variables affecting the performance of individuals could be different from those affecting the group.