Many of the 12 to 33 million artisanal (“small scale”) fishers in the developing world work at night using energy-intensive kerosene lanterns to attract fish to their nets. In Tanzania—where 100,000 such fishers operate, spending US$70 million per year on lighting—we identified current practices and conducted user-centered field tests of LED-based system usability, performance and energy savings potential, and estimated the market size for today's fuel-based lighting. Fishers in the areas we studied spend 35% to 50% of their take-home pay on lighting equipment and fuel. Due to the combination of higher intensity pressurized lanterns, and longer operating hours, Tanzanian fishers use as much lighting fuel as would about 1 million ordinary household lanterns. We found that similar catches could be obtained with battery-powered LED lighting systems, with a simple payback time for the LED system investment of three to four months. The fishers we interviewed were almost universally pleased with the concept behind the lights used in the field tests, and eager to purchase them provided the right price and performance. However none of the LED systems we tested were adequate for this use. Essential product modifications include improved durability and performance in harsh fishing environments. Independent testing and certification would encourage product quality and support consumer confidence as they adopt these highly beneficial new technologies. Our results provide a roadmap for product manufacturers and others interested in deployment, with an overnight-conversion market size of US$17 to US$21 million in Tanzania alone, plus US$6 to US$7 million per year in ongoing replacement expenditures. This potential could well justify retooling and marketing investment on the part of lighting manufacturers.