The use of antibodies to visualize the distribution and subcellular localization of gene products powerfully complements genetic and molecular analysis of gene function in Caenorhabditis elegans. Double and triple staining protocols are particularly useful for several reasons. First, colocalization of proteins either within tissues or at a subcellular level can be examined. Second, costaining with stage-specific or tissue-specific markers can define the timing and tissue specificity of antigen expression. For these types of studies it is useful to be able to collect data from multiple fluorescence wavelengths simultaneously. A confocal microscope equipped with a krypton/argon laser can simultaneously detect up to three different antigens. Using a confocal microscope it is also possible to collect a series of optical sections through a sample that allows observation of changes in distribution of the antigen in different focal planes of the tissue or cell.