Various components of the Goeckerman regimen were analysed. Although our findings are preliminary, they indicate several important observations: (1) Irradiation of tar treated patients with UVA compared to UVB showed the most efficacious wavelengths to be in the erythemic range (UVB). (2) A 1% concentration of crude coal tar was as effective as 5 and 25%.(3) Application of tar 2 h prior to irradiation was equivalent to overnight usage. (4) Little difference was noted between hydrophilic ointment and petrolatum as vehicles. (5) A tar gel was less beneficial than crude tar. The benefits of the Goeckerman therapy are derived from the intrinsic antipsoriatic effects of both tar and UVB. For some the combination is additive and necessary for clearing; for others either of the components may have great benefit alone. Our favourable results with UVB alone indicate that its effectiveness has been understated and poorly appreciated. Minimizing the time of tar application without loss of efficacy makes treatment adaptable to outpatient practice.