The aim of the study was to compare the efficacy of insulin glargine and aspart with NPH insulin and aspart in a basal bolus regimen in type 1 diabetes. In this 36-week randomised open-label two-period cross-over trial, subjects received 16 weeks' treatment with either once-daily insulin glargine or twice-daily NPH insulin after 4-week run-in. Primary outcome was HbA1c and secondary outcomes were fasting plasma glucose (FPG), weight change, incidence of hypoglycaemia, effect on lipid profile and patient satisfaction. Sixty patients with type 1 diabetes were recruited (33 male, mean age 42.7 years, mean HbA1c 8.53%) with 53 completing the study. At completion, HbA1c was lower with glargine and aspart than with NPH and aspart (8.07% versus 8.26%, difference -0.19 [95% CI 0.37-0.01]%, p=0.04). FPG was significantly different between glargine and NPH (p=0.002), with mean FPG on glargine 3mmol/L lower than on NPH at the end of the study. There were no differences in hypoglycaemia rate (p=0.63), weight (p=0.45) or lipid profile (p=0.18). Patient satisfaction was greater with glargine (DTSQ, p=0.001). Three patients discontinued as they wished to remain on glargine. We suggest that glargine combined with aspart is an effective basal bolus regimen in type 1 diabetes.