In recent years, the scientific community has provided many tools to assist with pathway analysis. Some of these programs can be used to manage functional annotation of gene products, others are oriented to exploring and analyzing data sets and many allow both possibilities. Potential users of these tools are faced with the necessity to decide which of the existing programs are the most appropriate for their needs. SerbGO is a user-friendly web tool created to facilitate this task. It can be used (i) to search for specific functionalities and determine which applications provide them and (ii) to compare several applications on the basis of different types of functionalities. Iterating and combining both functionalities can easily lead to selecting an appropriate tool. Data required by SerbGO is either the desired capabilities within a defined Standard Functionalities Set or the list of the tools to be compared. The analysis performed carries out a cross-classification that produces an easily readable output with the list of tools that implement the capabilities demanded or a table with the categorization of the GO tools that one wishes to compare. SerbGO is freely available and does not require a login. It can be accessed either directly at our server (http://estbioinfo.stat.ub.es/apli/serbgo) or at the GO Consortium website (http://www.geneontology.org/GO.tools.microarray.shtml#serbgo).