Safety, Tolerability and PK Study of Methylphenidate HCl ERCT in 4-5 Year Old Children With ADHD.

Inclusion Criteria: 1. Male or female child 4-5 years of age at screening. 2. Signed and dated informed consent provided by the subject's parent/legal and assent of the child (as applicable) 3. Meets DSM-5 criteria for ADHD based on the K-SADS-PL. 4. ADHD RS-IV Preschool-Home Version score at Screening and Baseline \>/= 90th percentile for gender and age in \>/=1 of the following: hyperactive-impulsive subscale, inattentive subscale, or total score. 5. Peabody Picture Vocabulary Test 4 (PPVT-4)Standard Score \>/=70. 6. Child Global Assessment Scale (CGAS) score \</= 55. 7. History of an adequate course of non medication treatment for ADHD based on investigator judgment or, where such treatments are not available, the severity of the subject's ADHD symptoms are such that medication treatment is deemed necessary by the investigator. Exclusion Criteria: 1. Treated with atomoxetine within 30 days prior to the Baseline. 2. Received any investigational products or devices within 30 days prior to the Baseline visit. 3. History of stimulant nonresponse, intolerability or hypersensitivity to any dose of methylphenidate or other stimulant.If a subject has a known allergy to D\&C red #30, he/she should not be enrolled in the study. 4. An intelligence quotient (IQ) \<70. 5. History of acute or chronic medical or psychiatric condition or cardiac or laboratory abnormality. 6. Less than 5th percentile for height or weight at Screening. 7. History of recent clinically significant self-harming behaviors.