A questionnaire sent to 325 U.K. dermatologists regarding toxicity of antimalarials had a 70% response rate. Hydroxychloroquine (HCQ) was used by 168 respondents, chloroquine (CQ) by 66, and mepacrine by 89 (only 111 always chose one of these). HCQ was considered to be the most effective by 59%, and to have the least cutaneous side-effects by 66%; mepacrine was considered to have the lowest frequency of ocular side-effects by 50%. Thirty respondents had encountered ocular side-effects, but in most cases these were mild. Maculopathy after short-term therapy was identified as a side-effect which is rarely considered. Ocular side-effects were believed to be due to cumulative dose alone by 31%, to dose/body weight alone by 8%, to duration of treatment alone by 3%, and to combinations of these by 58%. Overall, cumulative dose was considered relevant by 85%, duration of treatment by 52%, and dose/body weight by 41%. Referral for ophthalmology screening was always performed at baseline or after an initial trial of therapy by 56%; 17% never referred patients for baseline screening; 60% routinely requested ophthalmological follow-up. In comparison, 14% of respondents routinely referred patients for baseline ophthalmological screening before PUVA therapy (only 52% of whom routinely referred patients before antimalarial therapy). The most important factor contributing to an individual's current practice was experience in training posts (52%), followed by advice of local ophthalmologists (45%), personal experience (19%), specific publications (16%), and manufacturers' recommendations (14%).(ABSTRACT TRUNCATED AT 250 WORDS)