Biologic and physiologic factors associated with the availability of breast secretions by a nipple aspiration technique were investigated in 606 normal, non-lactating women. Data obtained on race, age, menstrual status, parity, contraceptive pill use, hormone use, and cerumen type indicated that availability of secretions was related to race, age, and menopause, and to genetic factors associated with apocrine bland function. Fluid aspirates were obtained most often from Caucasians (70.2% success), least often from Chinese (24.1% success). The percentage of successful aspirations declined in women over 50 years of age in all racial groups, but distinctly less so in Caucasians. Chinese and Japanese women with dry-type cerumen had a lower percentage of successful aspirations than those with wet type, which suggested that genetic factors may be associated with breast fluid secretion in nonlactating women.