The increased numbers of low birth weight (LBW) survivors has raised questions about the direct association between LBW and later diagnosis of Attention Deficit Hyperactivity Disorder (ADHD) in early childhood. A longitudinal data set was used to determine the relationship among perinatal morbidity and medical and neurological status during the toddler period (18 and 30 months) with lower attention and higher activity, cardinal features of ADHD at age 4. The sample of 39 full term and 149 preterm infants were recruited at birth. Infants were assigned to 1 of 5 groups based on perinatal morbidity. Medical and neurological status were classified as normal, suspect, or abnormal at 18 and 30 months. At age 4, five measures of attention and activity were gathered from parents and independent examiners. Multivariate analysis of variance (MANOVA) showed significant effects of perinatal morbidity, birth weight, gestational age, gender, socioeconomic status at infancy, and toddler medical and neurological status with lower attention and higher activity at age 4. Prematurity, perinatal illness, and later medical status are early markers for preschool behaviors associated with clinical diagnosis of ADHD.