A point source outbreak of Vibrio cholerae O1 El Tor Inaba infections occurred aboard an oil rig south of Port Arthur, Texas, in September 1981. Sixteen crew members had V. cholerae O1 infections as determined by serology or stool specimens; 15 were symptomatic. The high percentage of symptomatic infections was attributed in part to the ingestion of a large number of V. cholerae O1 organisms by susceptible individuals. Symptoms included diarrheal stools (100%), weakness (60%), abdominal cramps (53%), nausea (40%), and vomiting (27%). Only one of the three patients who sought medical attention was diagnosed by his physician as having cholera. Physicians who treat patients who live near or travel to the Gulf Coast should consider cholera in patients with watery stools. If cholera is suspected, laboratories should use thiosulfate-citrate-bile salts-sucrose (TCBS) agar in addition to routine enteric media for processing stool specimens.