OBJECTIVE To report a case of low grade papillary transitional cell carcinoma of the left renal pelvis in a young, heavy smoker of marihuana who denied cocaine use, alcohol intake and other habits. METHODS/RESULTS Intravenous pyelogram demonstrated a filling defect in the left renal pelvis and calyces. Biopsy revealed a urothelial carcinoma. The pathological analysis demonstrated diffuse low-grade non-invasive (Ta) papillary transitional cell carcinoma of the renal pelvis and calyces. Nephroureterectomy was performed. CONCLUSIONS This case indicates a cause-effect relationship between heavy and long-term marihuna smoking and transitional cell cancer. However, further cases from the literature or observations in larger populations are warranted.