In vitro studies provide mechanisms by which elevated lipoprotein (a) [Lp(a)] concentrations may promote both thrombosis and atherogenesis. Case-control studies have reported raised Lp(a) concentrations in patients with stroke, but prospective studies have failed to confirm the association. A potential confounding factor is that Lp(a) may rise acutely after stroke. We determined Lp(a) concentrations in 164 patients studied at least 21 days after stroke or transient ischaemic attack, and in 91 controls. In the patient group we correlated Lp(a) concentrations with both the degree of carotid stenosis estimated on duplex ultrasonography, and with stroke subtype (large vessel disease, lacunar infarction, and cardioembolic and unknown pathogenesis). There was no difference between Lp(a) concentration in cases and controls [median (quartiles) 0.10 (0.04, 0.39) versus 0.12 (0.04, 0.30) g/L, P = 0.34]. There was no difference in the proportion of cases compared with controls with a markedly elevated Lp(a) of > 0.4 g/L (21.3 versus 16.5%, P = 0.34). There was non-significant trend towards higher median Lp(a) concentrations in women [median (quartiles) 0.16 (0.04, 0.32) g/L versus 0.12 (0.04, 0.28) g/L, P = 0.3]. In view of this trend we analysed the differences between cases and controls for each sex separately. Lp(a) concentrations in men were median (quartiles) 0.08 (0.04, 0.26) g/L in the 101 cases and 0.12 (0.04, 0.28) g/L in the 43 controls (P = 0.6). Lp(a) concentrations in women were median (quartiles) 0.25 (0.04, 0.44) g/L in the 63 cases, and 0.16 (0.04, 0.32) g/L in the 48 controls (P = 0.16). Within the patient group there was no difference between Lp(a) concentrations in the different stroke subgroups. There was no relationship between Lp(a) concentrations and mean percentage carotid stenosis (rs = 0.14, P = 0.07). Our results suggest that in an unselected population of men studied more than 3 weeks post event there is no relationship between lipoprotein(a) concentrations and either stroke/transient ischaemic attack, or carotid atheroma. The relationship in women requires further study.