Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors (NRs) that control many cellular and metabolic processes. These proteins are ligand-activated transcription factors and three isotypes called PPARalpha, PPARbeta/delta and PPARgamma have been identified in lower vertebrates and mammals. They display differential tissue distribution and each of the three subtypes fulfills specific functions; however, all three PPARs affect energy homoeostasis and inflammatory responses. In addition, their activity can be modulated by drugs such as the hypolipidemic fibrates and the insulin sensitizing thiazolidinediones. Thus, understanding the biology and identifying small molecule modulators of the PPARs is an active area of research and may impact chronic diseases such as diabetes, obesity, heart disease and atherosclerosis. The PPAR Resource Page (http//ppar.cas.psu.edu) is a website devoting to keeping scientists up-to-date with the latest research on these proteins and provides links to a variety of public databases. The site was launched in 1998 to disseminate information about PPAR including cDNA sequences, protein alignments, DNA response elements (PPREs), and sources of cDNAs, proteins and antibodies. Recent additions include bioinformatics support such as gene expression microarray and pathway analysis links. As part of the Nuclear Receptor Resource (NRR, http//nrr.georgetown.edu/NRR/nrrhome.htm) some tools are shared with other constituents of this larger project. These include electronic publication, and a listing of scientists interested in the steroid and thyroid hormone superfamily. Receiving greater than 300 unique visits per week, the PPAR resource page has become a useful tool for researchers of these important NRs.