Abstract: We compared the transcriptome of yeast cells growing under steady-state conditions on twenty-one distinct unique sources of nitrogen. We found 506 genes differentially regulated by nitrogen and estimated the activation degree of all identified nitrogen-responding transcriptional controls according to the nitrogen source. One main group of nitrogenous compounds support fast growth and a highly active nitrogen catabolite repression (NCR) control. Catabolism of these compounds typically yields carbon derivatives directly assimilable by the cell metabolism. Another group of nitrogen compounds supports slower growth, is associated with excretion by cells of non-metabolisable carbon compounds such as fusel oils, and is characterized by activation of the general control of amino acid biosynthesis (GAAC). Furthermore, NCR and GAAC appear interlinked since expression of the GCN4 gene encoding the transcription factor mediating GAAC is subject to NCR. We also observed that several transcriptional regulations are active under a wider range of nitrogen supply conditions than anticipated. Other ones acting on genes not involved in nitrogen metabolism, e.g. the pleiotropic drug resistance (PDR) and the unfolded protein response (UPR) systems, also respond to nitrogen. We have completed the lists of target genes of several nitrogen-sensitive regulons and have used sequence comparison tools to propose functions for about twenty orphan genes. Similar studies conducted for other nutrients should provide a more complete view of alternative metabolic pathways in yeast and contribute to the attribution of functions to many other orphan genes.