We conducted an open-label study to test the effects of atorvastatin on serum lipids, lipoprotein(a) [Lp(a)] and plasma fibrinogen levels. A total of 90 dyslipidaemic, non-smoking patients (45 patients with primary hypercholesterolaemia and 45 patients with primary mixed hyperlipidaemia) aged 48 +/- 11 years were studied. The patients were treated with 20 mg of atorvastatin for 24 weeks, in a single nocturnal dose. At baseline and every eight weeks, the fasting lipid profile, together with serum Lp(a) and plasma fibrinogen levels (Clauss method), were measured. Atorvastatin was highly effective in normalising the serum lipid profile. No significant change in median serum Lp(a) levels was observed in the whole group of patients (0.14 g/l before, vs. 0.16 g/l after, treatment) as well as in patients with raised (> 0.30 g/l) baseline levels (n = 32). A small non-significant increase of plasma fibrinogen was found (3.04 g/l vs. 3.14 g/l) after 24 weeks of atorvastatin administration. The effects of atorvastatin on both these variables did not differ in patients with hypercholesterolaemia or mixed hyperlipidaemia. In conclusion, our findings suggest that the effect of atorvastatin on plasma fibrinogen levels in dyslipidaemic patients without evident vascular disease is not clinically relevant. Furthermore, any rise in fibrinogen levels that may occur is likely to be transient in nature. Further studies are necessary to clarify this issue. There was no evidence that atorvastatin influences serum Lp(a) levels.