In Taiwan, the high prevalence of emotional and behavioral problems in children has increased public awareness of young children's social-emotional development in recent years. Early identification of social-emotional delays for all young children, and subsequent early intervention (EI) with ongoing monitoring for children with special needs are critical. However, previous social norms regarding early mental health problems, the lack of social-emotional screening, and the scarcity of EI research on social-emotional development in Taiwan have resulted in lack of early social emotional screening and early identification. This study investigates toddler-aged children's social-emotional development in Taiwan and monitors their social-emotional behaviors over time. Two hundred eighty-four children with and without development delays were screened with a social-emotional screening tool, the Traditional Chinese ASQ:SE-2, and then were subsequently followed for six months and retested. Findings indicated a high positive rate of social-emotional risk at 22.9% for 18-month-old children who were not receiving early intervention services, suggesting that additional numbers of children could be identified for EI services early on. Findings also indicated that children with developmental delays or disabilities were 3 to 4 times more likely to have social-emotional risk, and that the risk could increase overtime, emphasizing the needs for monitoring social-emotional behaviors and the effectiveness of interventions. To address early identification and ongoing monitoring, the present study suggests the use of the Traditional Chinese ASQ:SE-2 and needs further studies establishing psychometric evidence for toddlers in Taiwan. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]