AbstractMurine susceptibility to ethyl carbamate‐induced carcinogenesis is strain dependent. In vivo sister chromatid exchange (SCE) responses to ethyl carbamate were evaluated in bone marrow cells of gravid adenoma‐susceptible (ICR/Jcl), and resistant (C57Bl/6J) and (DBA/2J) murine dams, as well as in liver cells of their respective ICR/Jcl, C57Bl/6J × DBA/2J (BDF1), and DBA/2J × C57Bl/6J (BDF), fetuses following a single intravenous injection of 1.1, 2.2, or 3.3 mmol/kg of ethyl carbamate on gestation day 13/14. Bone marrow tissues of C57Bl/6J and DBA/2J, but not ICR/Jcl dams, demonstrated greater sensitivity to SCE induction than liver cells of their respective fetuses. Furthermore, relative SCE responses in bone marrow among dams indicated greater sensitivity of the more tumor‐susceptible ICR/Jcl and C57Bl/6J strains to SCE induction by ethyl carbamate relative to the more tumor‐resistant DBA/2J strain. In addition, concurrent alterations (stimulation or inhibition) of bone marrow cell cycle kinetics by ethyl carbamate were consistent with hormone‐related, strain‐dependent hematopoietic stress dur