Meta-analysis techniques were used to summarize the results concerning gender differences reported in doctoral dissertations on visual spatial skills. Dissertations were chosen because they are not subject to the selection process of journals, which may bias results toward large effects. An analysis of 150 independent data points in 43 dissertations indicated an overall effect size of 0.205. A majority of these dissertations used college freshmen and sophomores as subjects. When the scores were partitioned into the categories of spatial perception, mental rotation, and spatial visualization, the effect sizes were 0.034, 0.433, and 0.171, respectively. These effect sizes are smaller than those reported in a recent meta-analysis of journal articles using the same ability categorization. When test results were recategorized using a task complexity scale, gender differences increased with the complexity of the task. When scores were partitioned by task complexity (recognition, manipulation, and multiple tasks), effect sizes were 0.131, 0.280, and 0.243, respectively. Within the spatial manipulation category, effect sizes became larger as the age of the subject increased. Four tables present the data. One appendix lists bibliographic information about the 43 dissertations, and two appendices classify the tests and list them by dissertation. (Author/SLD)