The effects on 31 normal subjects following exposure to sunbeds containing UVA lamps with minimal UVB emission have been compared in a double-blind study with the effects on nine control subjects of a similar exposure course three times weekly for 4 weeks to sunbeds emitting visible light. On previously untanned areas, all those subjects on active treatment developed a mild tan; in tanned areas they all developed a moderate tan, while all control subjects developed a minimal to mild tan. The mean protection factor against later UVB-induced erythema was 3.2±0.3 after the active course and 1.6±0.2 among the controls. Significantlsy more frequent adverse cutaneous effects for active subjects were pruritus, erythema, freckling, burning sensation, dryness and polymorphic light eruption. Cutaneous Langerhans cell numbers, and blood CD3+ (pan T-cell) and CD4+ (helper T-cell) lymphocyte subsets were reduced in both active and control groups. CD8+ (cytotoxic/suppressor T-cell) counts were significantly reduced in both groups. The changes found in both groups seem attributable to small amounts of UVB emission from both active and control lamps.