In May 1988, California became the first state to make aeromonas infection a reportable condition, thereby permitting the first population-based study of the epidemiology of infection caused by Aeromonas organisms. Case investigations were carried out on 219 of the 280 patients whose infections were reported during the first year of notification. The overall incidence rate for Aeromonas isolation was 10.6 cases per 1 million population. The gastrointestinal tract was the most commonly reported site from which Aeromonas was isolated (81%), with wounds being the next most common source (9%). Five (2%) of the 219 patients died; all five had serious underlying medical conditions apart from aeromonas infection. No common-source enteric outbreaks were reported. The high rate of gastrointestinal symptoms and isolation of organisms from medically vulnerable patients and the fact that other bacterial enteric pathogens were rarely isolated from symptomatic patients support evidence from previous studies that Aeromonas is an enteric pathogen. The evidence from these case reports in California suggests that aeromonas infections are not an important public health problem and are largely nonpreventable. Thus, public health surveillance is not necessary and mandatory reporting has been discontinued.