A meta-analysis of 14 quasi-experimental studies was conducted to compare the effect of size on various relaxation therapies applied to patients and health volunteer students. These studies were selected from theses, dissertations and papers that have been done between 1982 to 1993. Also They have a randomized or nonequivalent control group in a pre test-post test design. The studies were evaluated in different ways; 1) types of relaxation therapy, 2) total amount of time of relaxation therapy, and 3) types of outcome variables. For a group of homogenious studies, the weighted mean effect size and standard error were estimated. Some findings are summarized as follows : 1. Jacobson relaxation therapy had a larger effect on systolic and diastolic blood pressures than on state anxiety. 2. For the total time of relaxation therapy, (longer than 60 minutes) had a much larger effect in decreasing systolic and diastolic blood pressures than in the case of a time period shorter than 60 minutes. 3. Relaxation therapy applied to surgery patients also had a larger effect in decreasing state anxiety than when applied to other patients.