Objective: To evaluate the treatment effects of long-term growth hormone (GH) replacement therapy in adults with GH deficiency (GHD) who were followed in KIMS Germany (Pfizer International Metabolic Database), a national surveillance study. Design: The analysis was performed using baseline and long-term data (range: 4-10. years) of 440 consecutively documented patients (216 women and 224 men) with GHD, aged 20 to 49. years, enrolled in KIMS Germany. Serum insulin-like growth factor I (IGF-I), fasting blood glucose, fasting serum total cholesterol and low-density lipoprotein cholesterol (LDL-C) as well as body mass index (BMI), waist circumference (WC) and hip circumference (HC) at baseline and at last visit were studied. Furthermore, QoL-AGHDA score was determined to assess quality-of-life (QoL). Results: The mean dose of GH over all years was 0.41. mg per day in women and 0.37. mg per day in men. IGF-I and IGF-I SDS levels (standard deviation score) increased significantly (p < 0.001) during GH treatment. The QoL-AGHDA score decreased significantly (p < 0.001), indicating long-lasting improvement in QoL. In total cholesterol, LDL-C and fasting blood glucose, no significant changes were found. Only six patients developed type 2 diabetes during follow-up. Females and males similarly increased significantly in BMI, WC and HC. During GH treatment, recurrences of pituitary or central nervous system tumours or further de novo neoplasia were reported in 6 or 11 patients, respectively. The number of the most frequently reported GH treatment-associated adverse events was low. Conclusion: These observational data show long-term beneficial effects of GH replacement therapy on QoL and show no significant effects on total cholesterol, LDL-C or BMI, WC and HC. Additionally, our data indicate that GH replacement therapy in adults is well tolerated.