Twelve patients with nasopharyngeal carcinoma (NPC) were studied for spontaneous and phytohemagglutin (PHA)-stimulated production of cytokines, soluble markers and [3H] thymidine incorporation by mononuclear cells. The same number of patients with skin cancer and healthy subjects were used as control groups. Our results showed that the NPC group produced much more tumor necrosis factor-alpha (TNF alpha), soluble CD4 (sCD4) and CD8 (sCD8) in PHA-stimulated mononuclear cell supernatants than those in the other two groups. The levels of soluble interleukin-2 receptor (sIL-2R) and gamma-interferon (IFN gamma) in PHA-stimulated supernatants were at the same high level in the NPC and healthy subjects groups while the concentrations were much lower in the skin cancer group. We also noticed that the early stage group in NPC patients had higher levels of interleukin-1 alpha (IL-1 alpha), TNF alpha, IFN gamma and sIL-2R in both spontaneous and PHA-stimulated mononuclear cell supernatants. The stimulation index of PHA-responsiveness was 155, 5.2 and 37, respectively, in the healthy subjects, skin cancer and NPC groups. The PHA-responsiveness was depressed in both the NPC and skin cancer groups. It seems that cancer patients have an impaired T cell mitogenic response after mitogen stimulation. NPC patients had better immune response than skin cancer patients in immune factor release or PHA-responsiveness.