Background: Previous studies have identified preterm birth and/or small for gestational age (SGA) as risk factors for features of the metabolic syndrome, including high blood pressure, insulin sensitivity and atherosclerosis, occurring later in life, with controversial results. We conducted this population-based cohort study to investigate metabolic outcomes in those with former preterm birth and/or SGA status in Taiwan. Methods: Data were obtained from Taiwan's universal National Health Insurance Research Database. From 1996 to 2004, 37,119 preterm infants, 3386 SGA infants, and 162,020 matched controls were included. We investigated the risk of the metabolic disease, including hypertension, diabetes, and hyperlipidemia, which had been recorded by the end of 2008. Results: The preterm and SGA cohort, combined into one, had a significantly increased risk of developing metabolic disorders when compared with the comparison cohort (HR = 2.46, 95% CI = 2.02–3.01). We observed that children with former preterm and SGA status in Taiwan had a higher risk of developing hypertension (HR = 3.24, 95% CI = 1.58–6.67), Type 1 diabetes mellitus (HR = 1.80, 95% CI = 1.05–3.07), Type 2 diabetes mellitus (HR = 2.49, 95% CI = 1.98–3.14), and hyperlipidemia (HR = 2.14, 95% CI = 1.29–3.52). Conclusion: Our study revealed the risk of metabolic disease in those with preterm birth and/or SGA. Further studies with a longer duration of follow-up are required to confirm if there is a tendency for the metabolic syndrome to develop in this study cohort. Key Words: metabolic outcome, preterm birth, small for gestational age (SGA)