This article presents the results of two investigations, each measuring cellular immune function on 3 investigation days 1 week apart in 15 high and 15 low hypnotizable healthy subjects randomly selected for three groups: (1) a guided imagery group receiving instructions to enhance cellular immune function: (2) a relaxation group which did not receive instructions regarding the immune system, and (3) a control group. Study 1 investigated changes in monocyte chemotaxis (MC) and lymphocyte proliferative response (LPR) to three mitogens, while natural killer cell activity (NKCA) was measured in study 2. The results show similar patterns of brief decreases in LPR and NKCA immediately after intervention on all investigation days in both the imagery and relaxation groups. Increases in MC were found in both intervention groups on day 1. On a follow-up investigation day in study 2, a brief stress task yielded a slight increase in NKCA. In study 2, the control group showed decreases in NKCA similar to those observed in the two intervention groups. In general there were no significant changes in preintervention immune function throughout the investigation period. When comparing the effects in high and low hypnotizable subjects, we found that high hypnotizables showed greater decreases in LPR and NKCA than low hypnotizables. There are several inconsistencies between the results of the limited number of investigations studying the effects of guided imagery and relaxation on immune function. These differences may in part be explained by differences in methodology, time intervals between blood sampling, and subject characteristics such as age, health status and hypnotizability. The inconsistent results make it premature to make inferences about possible benefits of the application of these techniques in the treatment of immune related diseases, and further investigations are needed.