6 insulin-requiring diabetics were treated at home with continuous, long-term, dual-rate subcutaneous insulin infusion (CSII) by means of a portable syringe pump. The duration of infusion was 48--111 days. Patients were initially stabilised on CSII in hospital and then allowed home, where capillary-blood glucose control was monitored by the patients with glucose-oxidase reagent strips. Patients diluted and changed their own insulin for the pump, adjusting the dose according to the control achieved. Mean (+/- SD) blood-glucose values ranged from 4.8 +/- 1.6 to 7.5 +/- 1.6 mmol/l. In 1 longstanding diabetic insulin requirements fell from 92 U/day to about 35 U/day on CSII. 2 newly diagnosed juvenile-onset diabetics were also infused: in 1 patient requirements fell to zero after 48 days and in the other the dose fell to 14 J/day after 51 days of CSII. No cannula-site infection or significant palpable lipodystrophy was experienced. Patients treated with "open-loop" systems have little or no insulin reserve: potential loss of control--for example, during intercurrent illness-demands careful metabolic monitoring and prompt correction.