The Brook Reaction Test (BRT) is an objection word association test that provides an indirect measure of 22 personal interests. The purpose of the present study was to determine whether there were factors underlying 10 vocational interest categories on the BRT and a further category designated in the BRT Manual as 'unclassified'. The BRT was administered as part of a battery of selection tests to 325 males. The 1 1 scales were analysed using a principal components analysis and a varimax rotation carried out on the first six factors. The six factors identified accounted for 69.8 per cent of the variance and were largely bipolar in nature: Factor I, people vs. practical; Factor 11, unclassified interests; Factor 111, aesthetic vs. business; Factor IV, literary vs. secretarial; Factor V, biological sciences vs. agriculture; Factor VI, physical sciences vs. outdoor. A hierarchical cluster analysis applied to these 11 scales confirmed the factor solution and demonstrated the independence of the interest categories. Findings were related to: (i) three earlier factorial studies of the BRT; (ii) further evidence concerning its construct validity; and (iii) Holland's hexagonal classification of occupations and ACT-OCS work-task dimensions. Implications of the findings for practical test usage in guidance and selection are outlined, especially the necessity to score all the I 1 vocational scales.