The purpose of this study is to determine immune recovery and function after treatment with docetaxel or paclitaxel. Peripheral blood mononuclear cells were harvested before chemotherapy and at weekly times afterwards for cycle 1. Leukocyte subsets [CD45hiCD14lopolymorphonuclear neutrophils, CD45hiCD14himonocytes, CD45hiCD14−lymphocytes, CD3+CD4/CD8+T cells, CD3−CD19+B cells, CD3−CD16/CD56+natural killer (NK) cells], and circulating cytokine levels [tumor necrosis factor-&agr;, &ggr;-interferon (&ggr;-IFN), and interleukins (IL-2, IL-10, IL-12)] were followed. In addition, T-cell mitogenic function, NK function, and lymphokine activated killer (LAK) function was assessed. Ten patients were entered in the trial. T-cell frequency, B-cell frequency, and CD4/CD8 ratio did not change. IL-10 serum levels significantly decreased in paclitaxel-treated patients (4.4 ± 1.3 pg/ml at week 4 versus 7.8 ± 2.1 pg/ml at baseline;p< 0.05). IL-2, IL-12, and &ggr;-IFN levels were not detectable. NK cytotoxic activity decreased in docetaxel-treated patients. LAK cell activity was not altered. Four patients achieved a partial or complete response. They demonstrated higher than normal CD4:CD8 T-cell ratios and an improved phytohemagglutinin stimulation index (SI = 2.5). In conclusion, our findings suggest that immune function was affected more significantly after docetaxel treatment. Investigational approaches, which enhance cellular immunity, may be of greater relevance after treatment with docetaxel. Additional studies monitoring NK function after chemotherapy are recommended.