The correlative evidence linking elevated cholesterol to increased risk of cardiovascular disease is incontrovertible. Animal studies have shown that significant reductions in disease in humans may be forthcoming if blood lipids are reduced from elevated levels. Beginning in the 1960s, some patients had undergone a surgical bypass procedure for hyperlipidemia. Patients were selected for surgery after dietary management had been carried out for three years. The average serum cholesterol concentrations decreased markedly and the decrease was sustained.