Summary Commercial fishing is one of the most dangerous industrial activities. Overboard falls occur each fishing season, usually with serious, or even fatal, consequences. In recent years, two overboard deaths have occurred in Québec during lobster fishing activities. In general, the reported causes of overboard falls are loss of balance and being caught and dragged by fishing gear. The objectives of the research are to: 1) analyze the risks and determinants of overboard falls in lobster fishing, 2) document group and individual prevention solutions that can be adapted to lobster boats, 3) identify the most promising risk reduction scenarios. These objectives underlie a deep understanding of lobster fishing work. The study was conducted over a period of one year. An understanding of fishing was gradually acquired by analyzing responses to 1) a general risk-perception questionnaire (39 respondents: 22 captains and 17 assistant fishers) for the Gaspé and Îles-de-la-Madeleine regions, and 2) a descriptive questionnaire (14 respondents) administered to fishers who brought the researchers on board seven boats for 20 sea excursions. Videotapes and direct observation were done on board and then analyzed within the framework of real-work ergonomics. These tools were used to assess the risk of overboard falls in lobster fishing conditions, and to identify fall-related accident scenarios (and their circumstances) and the main risk factors. The results were discussed in validation meetings with the captains and fishers who took the researchers out on their boats. A follow-up committee of regional and sectorial fishing representatives guided the researchers throughout the study. This study highlights and segregates six working situations associated with the risk of overboard falls: three at the opening of the fishing season (loading the lobster traps, travelling from the dock to the fishing zone and dropping the traps in the water) and three during regular fishing (hauling the traps, moving the lines in the zone and dropping the traps back in the water). The initial launch is the riskiest situation, although it is infrequent, happening only once during the fishing season. The main risk factors are the weather conditions, crew attitudes and behaviours and working methods. The other two situations considered to be highest risk occur during regular fishing: dropping the traps, which is mainly done from the trap support table, and dropping them back in the water after the lines are moved in the zone. In this case, the traps are often handled not from the support table, but from the deck. The traps are dropped about 40 times a day (40 lines containing 7 to 10 traps each) per crew; the frequency with which the lines are moved in the zone varies greatly. The set-up of two important work stations, the support table and the hauler, have a significant impact on possible fall prevention strategies. The main solutions for improving the prevention of overboard falls are two-pronged: 1) Transferring research findings focusing on action with workers (sensitization, training and transfer of job knowledge and prevention knowledge); the knowledge and visual materials produced during this research may provide much material in this respect; 2) actions in terms of setting up “hauler and support table” stations. This original study incorporates, in its risk analyses, currently used and potentially applicable prevention strategies and methods, with reference to the general framework of real-work ergonomics. The research process mobilized two types of expertise: that of risk analysis and fishing researchers, and that of fishers in their capacity as daily risk-management experts.