The changing of disease patterns from infectious diseases to heart, cancer, and degenerative diseases needs advanced technologies to support diagnosis and to give therapies. The Automatic Clinical Analyzer (ACA) is one of modem laboratory equipments which continuously developed to enhance patient service outcomes. Previous researches showed its utilization rates varied 20-46.6% from total capacities per year. It indicated low utilization problems. So this research aimed patient characteristics and physician factors determining the utilization of the ACA. This was a descriptive study with a to-cross sectional design. Data were collected by interview to patients visited laboratories and physicians who referred patients for determine laboratory examinations using the ACA. The study was conducted in 2 (two) public hospital laboratories and 4(four) private clinical laboratories in Surabaya and Malang, East Java Province. Data were analyzed descriptively. Results showed that the patient characteristics who used ACA were higher proportion of those with older aged, women and senior high school to above education levels. Access to the services was also a determining factor of the ACA use because further distance increased transportation cost to reach the facilities. It also showed that the higher patient income received more services from the ACA and likely to visit private laboratories. From the physician view points, the factor determining the ACA use were that exmination results supported diagnosis, quickly be knew or received and easy to get. The study recommends to conduct further ACA studies associated with feasibility and effective cost to respond equity problems and the efficiency of ACA use.