Transforming growth factor-beta(1) (TGFbeta(1)) is thought to be an inhibitor of the keratinocyte hyperproliferation associated with psoriasis. The aim of this study was to evaluate plasma TGFbeta(1) and TGFbeta(2) concentrations in psoriatic patients as possible indicators of treatment efficacy. TGFbeta concentrations were measured in the plasma of 26 patients with psoriasis using an enzyme immunoassay and analysed with respect to the psoriasis area and severity index (PASI) before and after treatment with salicylic acid and/or sulphur followed by dithranol ointment. Baseline plasma concentrations of both TGFbeta(1) and TGFbeta(2) (20.3+/-2.2 ng ml(-1) and 0.14+/-0.02 ng ml(-1), respectively) did not differ significantly from control values (18.3+/-1.6 ng ml(-1) and 0.14+/-0.03 ng ml(-1), respectively). However, a significant positive correlation (r=0.69) between the baseline PASI and TGFbeta(1), but not TGFbeta(2), values was demonstrated. The pretreatment TGFbeta(1) concentration in patients with a PASI >/=15 (26.6+/-3.2 ng ml(-1)) was significantly higher than control values. There were no significant elevation of pretreatment TGFbeta(1) concentrations in patients with a PASI<15, or with respect to TGFbeta(2) in both groups. Treatment caused a significant decrease in TGFbeta(1), but only in patients with a PASI>/=15. Patients with baseline TGFbeta(1) concentrations exceeding the mean of the control group had a PASI value that was significantly higher than that of patients with a TGFbeta(1) concentration below the mean of the controls. These results confirmed an association between plasma TGFbeta(1) concentration and psoriasis severity, and demonstrated its normalization during treatment. Measurement of TGFbeta(1) in plasma should be considered as a possible biomarker of psoriasis activity during its management.