Many studies on the biochemical composition of the liquid aspirated from breast cysts have identified three types of cysts: type I (apocrine) cysts, with a high concentration of K+ and low levels of Na+ and C1-; type II (transudate) cysts, with an electrolytic content similar to that of plasma and high Na+ levels and, finally, type III cysts, with intermediate characteristics. The literature data appear to indicate that the women with type I cysts are at higher risk for breast cancer. The authors report the results of a study carried out on 143 women from October, 1991, through October, 1994, in the Radiology Department of the University of Bologna, to investigate the correlations between some risk factors for breast cancer, the characteristics of cyst fluid and the morphology of the cysts after pneumocystography. Of 186 cysts, 104 (55.9%) were type I, 49 (26.4%) were type II, and 33 (17.7%) were type III. Among the risk factors we considered, only the premenopausal state (41 to 45 years of age) exhibited a statistically significant correlation with the presence of type I cysts. The morphological study of the cysts after pneumocystography showed a surprisingly high correlation between the honeycomb pattern and type I cysts. The constant correlation between cyst morphology and electrolytic content may allow the easy identification of the subgroups of patients eligible for a closer follow-up.