Chiayi is a rural county located in southwestern Taiwan, and the effectiveness of its early intervention service system for autism spectrum disorders was studied in detail. A total of 71 children with autism spectrum disorders (n = 35) and developmental delay (n = 36) aged 2.5 years were referred from the only Early Intervention Reporting and Referral Center in Chiayi and followed up at 4 years. Results showed relatively low and varied services of early intervention for both groups during two time-point periods and a relative lack of specific early intervention programs for children with autism spectrum disorders. It was found, however, that cognitive abilities were increased for autism spectrum disorders and developmental delay groups. Additionally, the Early Learning Score at the initial evaluation could contribute to the high learner autism spectrum disorders subgroup. Parental socio-economic level was also determined to benefit the high learner developmental delay subgroup.