The authors attempted to induce hepatic veno-occlusive disease (VOD) in 64 dogs. Preparative treatments included combinations of total-body irradiation (TBI) or localized hepatic irradiation (LI) or both and chemotherapy consisting of dimethylbusulfan (DMB), L-phenylalanine mustard (L-PAM), methotrexate, or monocrotaline. VOD occurred infrequently in those dogs given 9.2 Gy TBI and DMB (1/10), TBI and/or LI (9.2-27 Gy) with L-PAM (2/36) or high dose methotrexate and LI (0/2). Specifically, VOD occurred in the dogs with a shorter interval between TBI and DMB or in the dog that received the glutathione reductase inhibitor, buthionine sulfoximide (BSO) before L-PAM. In contrast, among 17 dogs given monocrotaline, 8 developed VOD, particularly when used with L-PAM +/- irradiation (7/13). The major cause of death, early gastrointestinal toxicity, was further augmented by higher doses of irradiation, by shortening the interval between LI and L-PAM administration to less than 4 weeks, and administering BSO or monocrotaline before L-PAM. Gastrointestinal toxicity was lessened by giving low dose cyclophosphamide given before L-PAM. VOD can be produced in dogs especially with monocrotaline or BSO given before and L-PAM +/- irradiation. However, gastrointestinal toxicity renders the study of VOD beyond the acute phase difficult. Nevertheless, this approach appears useful for the study of VOD in other animals and for developing agents aimed at preventing VOD.