Two of the most common side effects of sclerotherapy of leg veins are telangiectatic matting (TM), and postsclerosis hyperpigmentation. A random sample of 113 female patients with similar treatment sites of telangiectasias (less than 1 mm in diameter) and venulectasias of 1-2 mm diameter on the legs were treated by sclerotherapy and assessed at 1 and 6 months later for the presence of TM and hyperpigmentation. Patients received treatment with either 23.4% hypertonic saline (HS) alone (N = 74), 1% polidocanol (POL) alone (N = 21), or a comparison treatment with both HS and 1% POL (N = 18). A subgroup of patients received both 1% POL and 0.5% POL (N = 10). The incidence of hyperpigmentation was related both to vessel size and to sclerosing solution; only one patient showed hyperpigmentation in a vessel less than 1 mm, while in 1-2 mm vessels the incidence was 10.9% for HS and 30.7% for 1% POL (p less than .004) at 1 month. At 6 months postsclerotherapy, the incidence of pigmentation was 2% for HS and 7.5% for 1% POL. Both the type and concentration of sclerosing solution affected the incidence of TM; the incidence of TM was 33% for 1% POL, compared to only 13% for HS (p less than .004). At 6 months follow-up, the incidence of TM decreased to 2% for HS and 9% for 1% POL. Ten patients who developed TM with 1% POL were treated subsequently with 0.5% POL and demonstrated no matting. These data indicate that the incidence of side effects was affected by both the concentration and type of sclerosant.