Abstract : We have performed high-throughput screening of low molecular weight chemical compounds to identify those that specifically inhibit the productive interaction between the c-Myc oncoprotein and its obligate heterodimeric partner, Max. The screening was facilitated by - the use of a micro version of a yeast two-hybrid assay in which the c-Myc-Max interaction induces the expression of beta-galactosidase. A screen of approximately 10,000 compounds identified seven that were able to inhibit beta-galactosidase activity. Testing of these in over 30 yeast strains expressing different transcription factors and their dimerization partners indicated that the observed c-Myc-Max inhibition was highly specific. Several of the compounds were also able to inhibit the growth of c-Myc oncoprotein-expressing Rat1 fibroblasts in vitro. Our results indicate that we have identified several low molecular weight compounds that are able to inhibit the activity of c-Myc-Max heterodirners. Plans for the next year include testing of these compounds to demonstrate in vivo activity against c-Myc induced tumors, as well as determining whether the compounds are effective at inhibiting the activities of the N-Myc and L-Myc oncoproteins.