Two water-soluble Fusarium metabolites, fumonisin B1 (FB1) and moniliformin (MN) were compared for their cytotoxicity in a variety of chicken primary cell cultures. Cardiac and skeletal myocytes and hepatocytes derived from embryos, and splenocytes, macrophages, and chondrocytes derived from 3- to 4-week old chickens were cultured in media containing either FB1 or MN (0 to 1 mM) for 48 hr. The colorimetric tetrazolium cleavage assay was then used for measuring cell survival. FB1 was not toxic to macrophages, hepatocytes, cardiac and skeletal myocytes but toxic to splenocytes and chondrocytes. MN was not toxic to chondrocytes and macrophages, but toxic to splenocytes, cardiac and skeletal myocytes. Median effective concentration (EC50) of MN in skeletal myocytes was 42 mu M (fiducial limits: 33 to 50 mu M) and in cardiac myocytes was 95 mu M (fiducial limits: 84 to 122 mu M). Estimated EC50 of FB1 in chondrocytes and splenocytes and EC50 of MN in splenocytes were all greater than 200 mu M.