Chemical approaches are widely used in directed differentiation of embryonic stem (ES) cells. In our search for novel lead compounds that could facilitate cardiomyogenesis of ES cells, we designed a two-step screening system based on P19 embryonic carcinoma and mouse ES cells. Application of this system to a quinazoline compound library including 2,3-disubstituted 8-arylamino-3H-imidazo[4,5-g]quinazolines and 2,6-disubstituted 4-anilinoquinazoline led us to the discovery of compound 62, which exhibits a stable cardiomyogenic effect on both P19 and mouse ES cells at a concentration of 0.1 μM. An EGFR inhibition assay and molecular docking studies confirmed 62 as a potent EGFR inhibitor with a tyrosine kinase IC(50) value of 101 nM. However, major differences in cardiomyogenic activity were observed between iressa and 62, indicating that other molecular events are also involved in compound 62-induced cardiomyogenesis of ES cells.