The South African science curriculum advocates an inquiry-based approach to practical work. Inquiry is a complex and multifaceted activity involving both cognitive and physical activity; thus, paper-and-pencil items do not provide the authentic context for this assessment. This study investigates the construct validity of inquiry-related questions in three national Grade 12 Physical Sciences examinations. Clarity about what is being assessed and how well a test samples a construct are critical to validity. The analysis that was guided by Stobart's conceptualisation of construct validity revealed that, to a large extent, inquiry-related questions exhibited threats to validity. The identified threats were categorised as contested validity, unclear validity and construct irrelevance. The findings of this study suggest that greater attention needs to be paid to the formulation of inquiry-related questions in written tests and examinations.