Hairless rats with dermatosis induced with a poor magnesium diet were previously shown to bear biochemical and immunological abnormalities. It was therefore felt of interest to investigate the spleen cells proliferative responses from these rats, both in the rash and the remission phases, when testosterone and parathormone plasma levels were also determined. Results showed that proliferative responses to mitogens and PTH levels were inversely related to the intensity of the dermatosis, whereas testosterone levels were more or less decreased. The role of 1.25 dihydroxyvitamin D3 in these modifications is questionable.