The effects of single doses of placebo, clemastine, ketotifen and prednisolone on chloroquine-induced pruritus were investigated in healthy black African volunteers using a visual analogue scale. There was no significant difference between the mean percentage degrees of pruritus recorded with placebo, clemastine and ketotifen. By contrast, the mean percentage degree of pruritus recorded with prednisolone was significantly lower than those with the other three treatments. If these results are confirmed in patients with malaria, it might be more rational to administer a single prophylactic dose of prednisolone in those who experience very disturbing pruritus with chloroquine.