[Guide for the classification of clinical research articles for the International Journal of Andrology].

The classification of knowledge is essential for understanding between researchers and the advancement of science. In this article a brief classification of clinical research methods is presented. The advantages that researchers use the same nomenclature are recalled, which enables improved communication among researchers, facilitates replication of studies and searches in databases, and helps to establish the aspects that can affect the different research models. They are grouped into four broad categories: epidemiological articles, articles of qualitative methodology, mixed methodology articles and review articles.