Serum electrolytes, creatinine, urea, protein, albumin, bilirubin and glucose were examined every 4 days until time of death in rabbits with VX-2 carcinoma implanted in one kidney. The rabbits were treated with doxorubicin, nephrectomy or combinations thereof and observed for up to 1 year. Rabbits treated with doxorubicin only showed a slight creatinine rise initially, but over time creatinine reached almost the same concentration as that in nephrectomized rabbits receiving equivalent doses of doxorubicin. Creatinine concentrations increased significantly above the normal range following nephrectomy combined with doxorubicin. Doxorubicin nephrotoxicity in rabbits occurs at lower doses than previously reported. In all rabbits the parameters except creatinine remained stable within the established normal ranges, except for the last 4 days before time of death in the animals with metastatic disease. Weight loss was the best parameter for making a prognosis for an individual rabbit, since peak weight was noted 16-20 days before death. In experimental work with VX-2 carcinoma, weight is thus the most important indicator of the time at which rabbits not responding to treatment can be put to death to avoid unnecessary suffering before the end of the experiment.