The purpose of this study was to examine the construct validity of the WOrk-reLated Flow inventory (WOLF; Bakker, 2008). This instrument was administered to 711 men and women who were working in Queensland, Australia. The results from the confirmatory factor analysis showed that the WOLF has moderately acceptable construct validity, with the three-factor model being a borderline fit to the data. Tests of the convergent validity of the WOLF yielded satisfactory results. However, the analysis of the discriminant validity of the WOLF showed that the instrument poorly discriminated between work enjoyment and intrinsic work motivation. Follow-up exploratory factor analysis, using recommended procedures for determining the number of factors to extract, revealed a two-factor solution, with the work enjoyment and intrinsic work motivation items loading on the same factor. Drawing on literature on psychological flow and motivation, as well as the findings of the present study, questions are raised over the adequacy of the conceptual basis of the three-factor model of work-related flow, the discriminant validity of the WOLF subscales, and the appropriateness of the wording of several of this measure's items. Using alternative methods and measures to investigate flow in work settings is recommended.