Aim: To determine the diagnostic yield of core needle biopsy in the diagnosis of palpable breast masses using open biopsy as the standard. Methodology: This was a prospective study lasting one year from February,2007 to January, 2008. Eighty-eight consenting female patients with breast masses who presented to the surgical clinic were enrolled into the study, interviewed, examined and investigated. Study subjects with suspected clinical malignant breast disease had their lesions staged according to the American Joint Committee on Cancer Staging (6thedition). The breast lesions were biopsied (by core needle biopsy using 16G core needles and open biopsy – incision or excision biopsy) by the researcher and the biopsy specimens submitted for histopathological examination by two histopathologists, one for each procedure. The resulting data was analysed with respect to the objective of the study. Results: A total of eighty-eight female patients were involved in the study, their mean age was 41.9 ± 16.2years with a peak incidence of breast disease between the third and sixth decades of life. There was a high literacy rate among the study subjects with 39(46%) having a graduate education, college education 26(30.5%), primary school 15(17.6%) while 5(5.8%) had no formal education. The AJCC stage of patients with malignant disease were as follows: AJCC stage 1 2(3.6%), AJCC stage IIa 4(7.1%), AJCC stage IIb 3(5.4%), AJCC stage IIIa 11(19.6%), AJCC stage IIIb 20(35.7%) AJCC stage IIIc 9(16.1%) and AJCC stage IV 7(12.5%). Of eighty-eight core needle biopsies, 12(13.6%) were non-diagnostic while 10(11.4%) were inadequate for histologic diagnosis. The remaining 66(75%) were adequate for histologic diagnosis. The diagnostic accuracy of core needle biopsy was 75%, sensitivity of adequate core needle biopsy 97.2%, specificity of adequate core needle biopsy 100%, positive predictive value 100% and negative predictive value 96.9%, false positive rate 0% and false negative rate 2.8%. Malignant, benign and normal tissues were represented in the histology of inadequate core needle biopsy with a preponderance of benign diagnoses. The histology of the adequate core needle biopsies showed an almost equal distribution between malignant and benign diagnosis. There was a preponderance of benign lesions among the non-diagnosticcore needle biopsies. There were no recorded complications among the subjects of the study. Conclusion: Adequate core needle biopsy is a reliable diagnostic tool in the diagnosis of palpable female breast masses