PhosphoGRID is an online database of experimentally verified in vivo protein phosphorylation sites in the model eukaryotic organism Saccharomyces cerevisisae. The database includes results from both high throughput (HTP) MS proteomics studies in addition to phosphosites identified in low throughput (LTP) studies of individual proteins or protein complexes. The identity of specific protein kinases and phosphatases shown to regulate appearance of phosphorylations are recorded, where available, as are the function(s) of the phosphorylation, and conditions under which the modification was demonstrated to occur.