Who is Eligible for the TODAY study? Children and adolescents with the following criteria may be eligible: Age 10-17 at the time of enrollment Diagnosis of type 2 diabetes by ADA criteria Duration of diabetes diagnosis less than 1.5 years at the date of referral BMI > 85th percentile documented at the time of diagnosis or during screening Fasting C-peptide at screening >0.6 ng/mL Absence of islet autoimmunity (both GAD- and ICA512-negative) A family member or adult closely involved in the childs daily activities agrees to participate in the childs study treatment Fluency in English or Spanish. Children with the following conditions CANNOT join TODAY: Genetic syndrome or disorder (other than diabetes) known to affect glucose tolerance Use of inhaled steroids at dose above 1000 mg Flovent equivalent Use of medication known to affect the metabolism of metformin or rosiglitazone Females who are pregnant, planning to become pregnant within two years of enrollment, or who admit heterosexual activity without appropriate contraception Incidence of DKA since diagnosis, unless due to a serious medical condition unrelated to their diabetes. For a complete list of inclusion criteria and exclusion criteria, click on these links.