Factors associated with restenosis were investigated in 107 patients undergoing carotid endarterectomy for symptomatic disease. The patients, 71 men and 36 women with mean age 68 ± 8 years, were followed up for 1 year by serial Duplex scanning. Carotid restenosis of ≥50% developed in 18 patients (17%), 11 men and seven women. Restenosis was not influenced by age, sex, diabetes or hypertension. Continuing smokers, serum cotinine >200 nmol/l, had a significantly higher incidence of ≥50% restenosis after 1 year (39%), compared with only 16% of non-smokers, p = 0.023. Restenosis ≥50% also was associated significantly with below median body mass index (p = 0.027). Women undergoing carotid endarterectomy had higher levels of cholesterol (median 7.4 mmol/l) and apolipoprotein B (median 0.81 g/l) than men (median cholesterol 6.4 mmol/l, median apolipoprotein B 0.69g/l), p < 0.01. For men only, restenosis of ≥50% was associated with low levels of serum cholesterol (median 5.7mmol/l), p = 0.002. For women cholesterol levels were higher (median 8.1 mmol/l) in those with ≥50% restenosis. Smoking adversely influences early restenosis (1 year) after carotid endarterectomy. Hyperlipidaemia is not a risk factor for restenosis in men, but may be associated with restenosis in women. © 1993 Grune & Stratton Ltd.