Forty-seven studies on the effects of patient teaching on knowledge, self-care behaviors, and metabolic control were analyzed using meta-analysis. Variables, such as type of patient instruction, type of research design, and overall quality of the study, also were analyzed. The 236 effect sizes had an unweighted mean of 0.91 (SD = 0.75) and a weighted mean of 0.33 (SD = 0.01). The weighted mean effect size for studies with control groups (N = 27) was 0.40 (SD = 0.05), and the weighted mean effect size for studies using the one group pretest-posttest design (N = 20) was 0.53 (SD = 0.05). Homogeneity analyses resulted in weighted mean effect size estimates for knowledge subvariables ranging from 0.41 to 0.91; for skill performance, 0.25 to 0.38; for compliance, 0.24 to 1.01; and for metabolic control, 0.06 to 0.84. Experimental mortality was the only variable significantly correlated with the overall weighted mean effect size, r = .52, p = .002. The results of this study clearly support the notion that patient teaching has positive outcomes in diabetic adults. Furthermore, methodological issues were important factors which influenced these findings.