New software tools and methodologies make claims that managers often believe intuitively without evidence. Many unsupported claims have been made about object-oriented programming. However, without scientific evidence, it is impossible to accept these claims as valid. Although experimentation has been done in the past, most of the research is very recent and the most relevant research has serious drawbacks. This paper describes an experiment which compares the maintainability of two functionally equivalent systems, in order to explore the claim that systems developed with object-oriented languages are more easily maintained than those programmed with procedural languages. We found supporting evidence that programmers produce more maintainable code with an object-oriented language than with a standard procedural language.