Over the past nine years, CMMC has recovered nine moribund California sea lions, suffering from primary and secondary complications due to metastatic, transitional cell carcinoma. Of the nine animals, five were male and four were female. All were sexually mature except one subadult male. The animals were found beached along Monterey, Santa Cruz, San Mateo and Sonoma County beaches. General physical appearances included enlarged or swollen hind flippers, abdominal distention, and prolapsed rectum. Four were considered under-weight, five were emaciated. All had a tumor located dorsocaudally between the kidneys. The primary tumor size ranged from 18cm to 3.0cm in length and 15 cm. to 0.5 cm in width. Sites of metastases varied but included lymph nodes, lung, liver, adrenal, spleen, ovaries, uterus, kidney, pancreas, bladder, mediastinum, peritoneum, and the visceral surfaces of the stomach and ilium. One specific site of origin for the cancer could not be determined. It is speculated that either one or more of the following are possible: bladder, ureter, adrenal, or lymph node.