['To assess the effects of weight gain on metabolic control, plasma lipids and blood pressure in patients with Type 1 diabetes.', 'Patients in the EURODIAB Prospective Complications Study (n = 3250) were examined at baseline and 1800 (55%) were re-examined a mean of 7.3 years later. Patients had Type 1 diabetes, defined as a diagnosis made before age 36 years and with a need for continuous insulin therapy within a year of diagnosis. Patients were aged 15-60 years at baseline and were stratified for age, sex and duration of diabetes.', "The change in HbA(1c) from baseline to follow-up examination was significantly more favourable in those who gained 5 kg or more during follow-up ('marked weight gain') than in patients who gained less or no weight or lost weight ('less or no weight gain'). In those with marked weight gain, there was a significantly greater rise in plasma triglycerides and total cholesterol and significantly less favourable changes in low-density lipoprotein and high-density lipoprotein cholesterol compared with those with less or no weight gain, with or without adjustment for HbA(1c). Systolic and diastolic blood pressure also rose significantly more in the group with marked weight gain."] Is weight gain associated with improved glycaemic control but with adverse changes in plasma lipids and blood pressure isn Type 1 diabetes?