Abstract An experiment was conducted to study how different methods of indentation affect the ability of programmers to understand programs. The subjects were 72 students from an intermediate programming course. Each subject received one of three implementations of a short Pascal program. Each implementation used a different method of source code indentation: no indentation, “excessive indentation”, and Purdue University Department of Computer Science standard (moderate indentation). The subjects answered a 10-question test about the program. The scores of those subjects who received the program written in the departmental standard were better than the scores of the other two groups.