Hospital transfusion services and blood centers have continued to use manual hemagglutination methods for most of their pretransfusion compatibility testing. Automation with continuous-flow and batch analyzers has been practical only for the largest blood-processing centers. During the past 20 years, other methods of streamlining compatibility testing have evolved. Two of the most successful approaches have employed microplates to perform either liquid agglutination tests or solid-phase red blood cell adherence tests. Increasing numbers of automated systems for compatibility testing, based on these technologies, have become commercially available. These systems were optimally designed for batch processing. More recently, dipsticks for ABO grouping and direct antiglobulin testing have been developed, which were ideally suited for individual testing.