Summary: To analyze if learning Technical Drawing improves the spatial visualization aptitude, a visualization test was applied, at the beginning and at the end of a Technical Drawing course, on a sample of first year engineering students. At the end of the Technical Drawing course, it was observed that more than one third of the students increased their performance on the visualization test. This improvement was statically significant and equal both for men and women. These results support the conclusion that spatial visualization is an aptitude that could be improved with training and, although teachers do not explicit this objective, Technical Drawing courses are an efficient way of doing this. It can be suggested that the change in spatial visualization aptitude may be considered as an efficiency indicator of the teaching-learning process.