As their life expectancy has improved, patients with cystic fibrosis (CF) have experienced an increasing incidence of diabetes. Hyperglycemia may adversely influence weight, pulmonary function, and development of microvascular complications. Strict control of blood glucose has not universally been sought, however. A program of multiple daily insulin injections and self-monitoring of blood glucose with an aim of normoglycemia is described in this article. The typical cystic fibrosis diet is variable in quantity and features a preponderance of simple carbohydrates; this is contrary to the usual diabetes meal plan. We describe the use of a flexible meal-planning system to establish individualized carbohydrate targets with specific insulin boluses titrated to each meal to control postprandial blood glucose excursions. Records of 22 patients followed for more than 1 year are reviewed. Mean (+/- standard error of the mean) glycosylated hemoglobin was reduced from 11.3 +/- 3.1% (at baseline) to 8.1 +/- 1.8% (at 1 year). Mean percent of ideal body weight also increased from 95.4 +/- 15.2 to 100 +/- 17.1. We conclude that strict metabolic control is an attainable goal in patients with cystic fibrosis and is associated with positive weight gain.