Purpose: PCNA has been widely used because it is highly accurate, relatively simple and safe to administer.Regardless of its high diagnostic rate, PCNA has the difficulty in excluding malignancy in the cases of "negative for malignancy" results in PCNA cytologic reports. So, we analysed PCNA cases to evaluate the clinical outcome of "negative for malignancy" results in PCNA cytologic reports. Materials and Methods: PCNA in 170 cases were done between January, 1991 and December, 1993, and the diagnosis was malignancy in 86 cases, specific benign disease in 30 cases, "negative for malignancy" in 45 cases and inadequate sample in 9 cases. We analysed 36 cases among 45 cases of "negative for malignancy" results in cytologic examinations. The final diagnosis was made on the basis of histopathologic examinations, radiologic findings and clinical courses. we compared the final diagnosis to the radiologic diagnosis. Results: Of the 36 cases with initial "negative for malignancy" results, the final diagnosis was benign in 30 cases and malignant in 6 cases(17%). In radiologic diagnosis of the malignancy, "positive predictive value" was 42%, "negative predictive value" was 96%, and accuracy was 78%. Conclusion: In the cases of PCNA results of "negative for malignancy", malignancy can not be excluded because 17% of the cases are proved tobe malignant. And if malignancy is highly suggested at radiologic examination, the possibility of malignancy is 42%, and so intensive follow-up examination is needed.sibility of malignancy is 42%, and so intensive follow-up examination is needed.