Androgens regulate the physiology of motor neurones both during development and in adult life. In particular, androgens increase the rate of axonal regeneration after axotomy, an effect correlated with the up-regulation of tubulin. In order to determine whether this was the result of a direct hormone action on neurones, we examined the effect of testosterone on microtubular proteins in human neuroblastoma SH-SY5Y cells. Treatment of proliferating SH-SY5Y cells with testosterone resulted in an up-regulation of alpha- and beta-tubulin. By contrast, no change in tubulin was observed either in cells differentiated into a neuronal phenotype by retinoic acid or in adrenal SW13 cells. We also show that an up-regulation of the ubiquitous beta(II)-tubulin and of the neurone-specific beta(III)-tubulin isoforms contributes to the overall increase in tubulin in response to androgen treatment. The increase in tubulin levels following testosterone treatment was abolished by co-incubation with antiandrogens, indicating that this effect is mediated through a classical mechanism of steroid action. The two microtubule-associated proteins, tau and MAP2b, remained unchanged following testosterone exposure. Thus, these results demonstrate that tubulin is a direct neuronal target of androgen regulation and suggest that dysregulation of tubulin expression may contribute to the pathogenesis of some motor neuronopathies.