A line of chick embryo cells (CEC) was obtained from CEC treated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The cells, designated CHCC-OU2, were contact-inhibited, formed no colony in soft agar and did not produce tumors when inoculated into syngeneic chickens. The electron microscopic examination and reverse transcriptase assay showed no virus production from the cells. Subgroup A avian sarcoma virus (ASV) and Newcastle disease virus replicated well in the cells of this cell line.