Some 8059 healthy women (mean age 58 years) were studied in 1973 with the aim of establishing the presence or absence of a variety of physical and psychological risk factors for mammary cancer. Mortality was established in 1988. factor predictors were highly significant. Physical risk factors were more predictive than psychological ones, but both interacted synergistically to predict mortality. Alone, psychological (stress) factors had little effect, while-physical factors did. However, psychological factors seemed to potentiate the effect of physical factors, particularly in the middle range. The causal relevance of psychological factors was established in a special intervention study using autonomy training as a method of prophylactic therapy and comparing outcome with the effects of no therapy (control).