To evaluate the expression of estrogen receptor beta (ERbeta) in fine needle aspirates (FNAs) and correlate the findings with its expression in tissue sections.In 38 cases of breast carcinoma, expression of estrogen receptor alpha (ERalpha) and ERbeta in aspirates and tissue sections was correlated with the cytologic and histologic grade of the tumor.ERalpha and ERbeta were expressed as nuclear staining in 80% and 90% of the cases in tissue sections and 47% and 45% of the cases in aspirates, respectively. Tissue expression of ERalpha (grade 1, 81%; grade 2, 100%) and ERbeta (grade 1, 94%; grade 2, 100%) was greater than in grade 3 tumors (ERalpha, 50%; ERbeta, 70%). In FNAs they were equally distributed in the different cytologic grades. In aspirates 30% of ERalpha negative tumors were positive for ERbeta, while in tissues 75% of ERalpha-negative tumors were positive for ERbeta (p = 0.007).Demonstration of ERbeta on FNA smears is feasible. It helps identify the specific subcohort of ERbeta-positive tumors in ERalpha-negative breast cancers; that may have therapeutic importance.