Background. Hypercholesterolaemia is initially treated by diet. However, most studies of diet and cholesterol response have been carried out in men, and it is not known whether women react to diet to the same extent as men do. We therefore studied sex differences in the response of serum cholesterol and lipoproteins to diet. Materials and methods. We measured the responses of serum cholesterol to a decrease in dietary saturated fat in seven trials involving 126 men and 147 women, to a decrease in dietary trans fat in two trials (48 men and 57 women) and to a decrease in dietary cholesterol in eight trials (74 men and 70 women). We also measured responses to the coffee diterpene cafestol, which occurs in unfiltered coffee, in nine trials (72 men and 61 women). All subjects were lean and healthy. Results. The response of total cholesterol (± standard deviation) to a decrease in the intake of saturated fat was greater in men (-0.62 ± 0.39 mmolL-1) than in women (-0.48 ± 0.39 mmolL-1; 95% confidence interval, 0.04-0.23 mmolL-1). The response of total cholesterol to a decrease in the intake of cafestol was also larger in men (-1.01 ± 0.49 mmol L-1) than in women (-0.80 ± 0.49 mmolL-1; 95% confidence interval, 0.04-0.39 mmolL-1). Responses to traits fat and to dietary cholesterol did not differ between men and women. Conclusion. Men have larger responses of total and low-density lipoprotein cholesterol to saturated fat and cafestol than women do.