The question of what types of parameters should be employed in establishing adequacy guidelines for fine-needle aspirations (FNAs) of palpable breast lesions remains without consensus opinion among cytopathologists. Although some investigators have suggested guidelines, based largely upon cellularity standards, these have been somewhat conflicting, and the overall issue of whether or not cellularity is an appropriate measure of adequacy is controversial. This study examines the number, size, and composition of cell clusters in FNAs of palpable breast masses which had surgical follow-up, in an effort to identify characteristics of diagnostic aspirates which could contribute to adequacy guidelines. Seventy-seven consecutive cases with surgical follow-up were selected from four quality-assurance (QA) categories (true positive, TP; true suspicious, TS; true negative, TN; and false negative, FN). All cases were evaluated in terms of overall cellularity (numbers of cell clusters), proportions of different-sized epithelial clusters (small, medium, and large), and proportions of epithelial to fibrofatty elements. Although the FN category showed the lowest average cellularity, the application of cellularity cutoff values as a condition of adequacy would have resulted in conspicuous numbers of cases from the "true" categories (TN, and to a lesser degree TS and TP) being rendered inadequate. For example, if cases with fewer than six epithelial clusters were excluded by virtue of inadequacy, 69% of the FN cases would have been affected, along with 40% of the TN, 6% of the TS, and 4.5% of the TP. In terms of composition of the aspirate, neither proportions of the differently-sized epithelial clusters nor ratios of epithelial:fibrofatty elements reliably distinguished the "true" from the "false" diagnoses. This study concluded that quantitative parameters alone are insufficient measures for determining specimen adequacy in FNA of palpable breast lesions. Rather, adequacy remains based upon factors such as confidence of needle placement, cell preservation, and correlation with clinical and mammographic findings. Diagn. Cytopathol. 1999;21:105-111.