The evidence suggests that, compared with NPH insulin, insulin glargine is effective in reducing the number of nocturnal hypoglycaemic episodes, especially when compared with once-daily NPH. There appears to be no improvement in long-term glycaemic control and therefore insulin glargine is unlikely to reduce the incidence of the long-term microvascular and cardiovascular complications of diabetes. Further research into insulin glargine is needed that addresses the quality of life issues associated with fear of hypoglycaemia and also the economic impact of balance of HbA1c control and incidence of hypoglycaemia achieved in practice. Studies examining the economic evidence on insulin glargine should be published.