G protein-coupled receptors are essential components of the pheromone signaling pathway in Saccharomyces cerevisiae. When ligands bind to these receptors, their down regulation is stimulated. The sequence of events in this process is proposed to be the following: ligand-induced conformational change, receptor hyperphosphorylation and ubiquitination, internalization by an actin-dependent mechanism and subsequent delivery through at least two endocytic intermediates to the vacuole where the receptors are degraded.