Beta‐hydroxyproplonitrile (β‐HPN) was incorporated in the drinking water of rats in order to define the toxicological effects associated with repeated daily exposure to this compound. Parameters evaluated were appearance and demeanor, mortality, body weight, food consumption, water consumption, hematology, terminal organ weights and organ to body weight ratio, and gross and microscopic pathology of tissues. No untoward effects were associated with the ingestion of β‐HPN at the dose levels utilized.