A newly developed battery cycler for cycling rechargeable nickel/cadmium cells of the type used in personal sampling pumps was evaluated. The cycler operated by discharging a nickel/cadmium battery pack to 3.9 volts per cell and then recharging the batteries at a high rate, 10 percent of their rated ampere hour capacity, for 14 hours. The cycler was tested by cycling 17 used battery packs, each battery having a 5 volt, 1200 milliampere hour capacity. The battery packs were given a full charge before being cycled. Four sets of batteries were cycled at different times, the first two sets having five batteries and the other two sets containing six batteries. The effects of the cycling were evaluated by determining the capacity of the batteries after three discharges. The capacity of five batteries was increased significantly, showing increases in capacity of 10.6 to 49.8 percent. The capacity of two increased slightly, showing increases of 5.3 and 7.8 percent. Nine batteries were not affected by cycling and one battery deteriorated. The authors conclude that cycling of used nickel/cadmium batteries is beneficial on a short term basis, and that further studies are required to determine if cycling should be conducted on a routine basis. A circuit diagram of the cycler was appended.