Objective: To find out the incidence of wound infection in patients with HIV and reduced counts of CD4 lymphocytes., Design: Open study., Setting: University hospital, Spain., Subjects: 70 patients with HIV infection and enlarged lymph nodes., Interventions: Biopsy of lymph nodes and withdrawal of a sample of blood for counts of CD4 lymphocytes and neutrophils., Main Outcome Measure: Development of infection at the biopsy site, and correlation of infecting organism with culture taken at the time of biopsy., Results: Patients were divided into three groups depending on their CD4 count: more than 500 cells/ml (n = 26), 200-500 cells/ml (n = 24), and less than 200 cells/ml (n = 20). Their neutrophil counts were 5.1, 3.8, and 2.5 x 10(9)/1, respectively. There were found four wound infections (6%); 2 were in the group with more than 500 CD4 cells/ml, and these were caused by Staphylococcus aureus (which had been grown from nodes in 6 patients at the time of biopsy). The other 2 were in the group with less than 500 cells/ml and these were caused by Mycobacterium tuberculosis; cultures of the nodes had shown Staphylococcus epidermidis (n = 3) and M tuberculosis (n = 17). There were no infections in the group with 200-500 CD4 cells/ml, in which S epidermidis (n = 5) and M tuberculosis (n = 8) had been cultured from the lymph nodes., Conclusions: The CD4 count was of no prognostic importance in the development of wound infection, but severe depression of the CD4 count may increase the risk of atypical wound infections.