The effects of 2,5 hexanedione (2,5 HD), a metabolite of n-hexane, were investigated in different in vitro systems. A human mammary carcinoma cell line, a human melanoma cell line, and fetal mouse neuronal cells in primary culture were considered. Light and electron microscopic observations demonstrated clearly that changes in cell proliferation can be detected. Furthermore, morphologic differentiative phenomena characterized by a noticeable increase in cell protrusions and dendriticlike processes can occur. Differences in the features of these processes were also detected between the different cell lines. These data can indicate non-neuronal cells as possible further targets of the toxicant. The possibility could be hypothesized that toxic neuropathies are generalized disorders, being neuronal system exceptionally vulnerable to 2,5 HD. Moreover, results obtained suggest that the sensitivity of in vitro systems could represent a useful tool in studying the mechanisms of action of the neurotoxicant 2,5 HD.