Serum alpha 1-acid glycoprotein (alpha 1AG) concentrations were determined in 55 dogs with previously untreated, histologically confirmed, high-grade lymphoblastic lymphoma, and in 34 dogs with histologically confirmed nonhematopoietic malignancies (13 dogs with carcinomas and 21 dogs with sarcomas). Serum concentrations were again determined in 32 dogs with lymphoma that were in complete remission 3 weeks after 1 dose of doxorubicin (30 mg/m2 of body surface, i.v.) and in 22 dogs that were still in complete remission 3 weeks after a fourth dose of doxorubicin. For comparison, serum alpha 1AG concentrations were measured in 19 clinically normal (control) dogs of similar weight and age. Eight of the control dogs were given 1 dose of doxorubicin (30 mg/m2, i.v.), and serum alpha 1AG concentrations were measured 3 weeks later. In control dogs, mean serum alpha 1AG concentration after treatment with doxorubicin was not significantly different from mean concentration before treatment. Mean alpha 1AG concentrations in untreated dogs with lymphoma, in dogs with sarcomas, and in dogs with carcinomas were all significantly higher than mean concentration for untreated control dogs. In addition, the mean concentration for dogs with osteosarcomas was significantly higher than mean concentration for untreated control dogs. There were no significant differences in mean serum alpha 1AG concentrations among dogs with different clinical stages of lymphoma (stage IIIa, stage IVa, stage Va). However, mean serum alpha 1AG concentrations were significantly increased for dogs with stages IIIa, IVa, and Va lymphoma, compared with mean concentration for untreated control dogs.(ABSTRACT TRUNCATED AT 250 WORDS)