OBJECTIVE: To evaluate the usefulness of our original liquid-based cell preparation system AMAPS (aspiration material preparation system) and to compare it with the AutoSmear system in breast aspiration cytology. STUDY DESIGN: A total of 487 specimens of fine-needle aspiration cytology of the breast were retrieved, of which 250 were processed with AMAPS and 237 with the AutoSmear method (before the introduction of AMAPS). A final histological diagnosis was obtained by an excisional biopsy or a surgical resection in 148 cases. RESULTS: Cell recovery rates were significantly improved with AMAPS (96.8 and 99.1% in Papanicolaou and Diff-Quik, respectively) compared with the AutoSmear method (40.9 and 42.3%, respectively; p<0.01). Within-run and day-to-day reproducibility of cell recovery was satisfactory, with coefficients of variations of 6.8 and 8.7%, respectively. Following the introduction of AMAPS in breast cytology, the unsatisfactory rate decreased significantly (from 16.0 to 8.8%; p<0.01), while the diagnostic sensitivity for malignancy did not change (97.8 to 98.1%). Moreover, the diagnostic specificity for benign lesions increased from 75 to 93.8%, thus decreasing the excision rate of fibrocystic disease. CONCLUSION: AMAPS may serve as an alternative to the conventional technique or commercially available liquid-based cytology systems.