The ability of normal and clumsy children to match the length of lines within and between the modalities of vision and kinesthesis was studied. The clumsy children showed perceptual impairments, as indicated by their poor performance on the visual, kinaesthetic and cross-modal judgements of length and also by their low scores on spatial subtests of the WISC. Variations in motor skill correlated with performance on the visual perceptual measures, but not with performance on the kinaesthetic or cross-modal tasks. The idea that clumsiness may be caused by an impairment of visual perception is discussed, together with some alternative interpretations of this pattern of results.