Abstract Objective To observe any changes in serum concentrations of lipids, when UK meat-eaters switch to a self selected vegetarian diet for 6 months. Design Observational study using capillary blood samples and 3-day estimated dietary diary. Setting Free-living subjects in the North-West of England. Subjects Twelve male and 31 female adult volunteers aged between 18 and 42 years. Outcome measures Serum lipids; nutrient intake and anthropometric measurements at baseline and 6 months after switching to a self-selected vegetarian diet. Results Total energy intake and amount of energy derived from saturated fatty acids decreased significantly after changing to a vegetarian diet (P < 0.05) whereas energy derived from carbohydrate, and intakes of nonstarch polysaccharide intake increased. On switching to a vegetarian diet, total cholesterol and triacylglycerol concentrations were not significantly changed, but HDL-C was 21% higher than at baseline (1.21 mmol L−1 vs. 1.47 mmol L−1; P = 0.001). Conclusions These results suggest that beneficial changes to diet occurred on changing to a self-selected vegetarian diet. Changing to a self-selected vegetarian diet appears to be one way of achieving a better blood lipid profile.