A spatial-skills test is used to examine the effect of GIS learning on the spatial thinking ability of college students. Eighty students at a large state university completed pre- and post- spatial-skills tests administered during the 2003 fall semester. Analysis of changes in the students' test scores revealed that GIS learning helped students think spatially. These improvements were the result of the connection between students' GIS activities and experiences and the tested spatial thinking skills. Strong correlations were observed between the participants' spatial thinking and their achievement in the GIS course. (Contains 5 tables and 4 figures.)