We previously demonstrated that anaesthetics affect leukocyte response by inhibiting lymphocyte capping and metabolism and the phagocytic activity of neutrophils in some experimental models. In the present study, we investigated the effects of the clinical use of three different types of anaesthesia on lymphocyte subset distribution and activity: inhalational anaesthesia (isoflurane), a neuroleptoanalgesia, or local anaesthesia was used in patients submitted to the same operation (hysterectomy). At time 0 (before administering the anaesthesia) and at 10 min and 48 h from the start of the operation, heparinized blood was obtained from each of the 30 patients studied; three lymphocyte subpopulations were isolated (CD4+, CD8+ and CD19+). Cell number was identified for each lymphocyte subset, and (as an indication of cellular function) the intracellular contents of ATP and cAMP were evaluated by luminescence methods. The relevant results for each of the 3 anaesthetic methods were as follows: i) treatment with isoflurane induced a significant reduction in the number and function of CD4+ cells at 10 min, which was reversed at 48 h; a functional but not reversible decrease of CD19+ cells was obtained, ii) treatment with neuroleptic drugs induced a significant progressive functional impairment of CD4+ and CD19+ cells, and iii) local anaesthesia caused a significant functional impairment of CD8+ cells at 48 h and a significant functional impairment of CD19+ cells at 10 min and 48 h.