A comparison was made between reuse of plastic disposable needle-syringe units and glass syringes with daily new needles in diabetic patients who take daily insulin injections. Parameters studied were incidence of infection, clarity of syringe readings, ability to use syringe, and sharpness of needle. The plastic disposable units could be reused with safety and patient satisfaction by most patients for at least 3 days. Considerable cost benefit could accrue if disposable units were used more than one time for insulin injections.