Most patients with cystic fibrosis (CF) and pancreatic insufficiency require supplementation with fat-soluble vitamins to maintain normal serum levels. Even with supplementation, toxicity is rare. We evaluated serum vitamin A and E levels in 23 adult patients with CF who underwent double lung transplantation. Twenty-one of the subjects were pancreatic insufficient. Fifteen subjects had serum vitamin levels before and after transplant. The median time posttransplantation for these subjects was 9 months. Mean serum vitamin A and E levels were significantly higher posttransplantation (P<0.0001, P<0.001, respectively). Eight subjects who only had posttransplant vitamin levels also had abnormally high vitamin A levels. Although the etiology of this novel finding is unclear, possibilities include altered absorption, drug interactions, impaired retinol metabolism, or increased hepatic synthesis of retinol binding protein.