Little is known about the influence of acupuncture treatment on the immune system. The respiratory burst (RB) of polymorphonuclear leukocytes (PMN) is a recognized measure of their cytotoxicity, an important component of the immune system. The present trial was therefore performed to examine whether a single-acupuncture treatment has an immediate effect on the RB of neutrophil PMNs. Sixteen volunteers were enrolled in the study. After randomization, eight volunteers were treated bilaterally with standard needles at acupoint LI11 and eight volunteers with placebo needles at the same acupoint, each for 30 min. The RB was determined before and 30 min after treatment. After two weeks, each group received the alternative treatment. There was a drop-out of two volunteers. No period or carryover effects were found in the remaining fourteen volunteers. No effect of acupuncture on the neutrophil RB was observed.