An 8-yr-old intact male woma python (Aspidites ramsayi) presented for a caudal coelomic mass effect of 3 wk duration. Ultrasound and fine needle aspiration with cytology failed to identify the source of the mass. Exploratory surgery found a 10-cm diameter, lobulated, cystic mass closely associated with the left kidney. Tumor resection with left adrenalectomy and left nephrectomy was performed. Histopathologic examination identified an adrenal interrenal cell (cortical) adenocarcinoma with adjacent renal fibrosis. The snake recovered from surgery uneventfully and was clinically healthy over an 18 month follow-up period. Eleven months postsurgery a contrast-enhanced coelomic computed tomography scan was performed to evaluate the snake for metastatic disease or local recurrence. No metastases were identified, but local recurrence was not definitively ruled out and continued monitoring of the surgery site was recommended. Eighteen months postsurgery an ultrasound examination of the snake revealed significant tumor regrowth. Because of the recurrence of disease, no further treatment was pursued.