A technique for extracting DNA from archival and fresh tissue from fine needle biopsy (FNB) samples for the polymerase chain reaction (PCR) is described. The method was used to detect the bcl-2 oncogene in various cytologic lymphoid preparations. The DNA was amplified with primers specific for the major break point region of the t(14;18) translocation, and the presence of the bcl-2 oncogene was correlated with clinical, cytomorphologic, histologic and immunologic findings. Thirty patients who had FNB of lymphoid tissue were randomly selected, 18 retrospectively and 12 prospectively. Bcl-2 was present in 3 of 8 cases of reactive lymphadenopathy and 9 of 22 cases of non-Hodgkin's lymphoma. Of these, seven had follicular small cleaved cell lymphoma, and two had large cell lymphoma. Smears, both archival and fresh, and cell suspensions provided sufficient DNA for PCR amplification. The technique has potential applications in several areas of cytologic and hematologic practice.