Abstract. Reactive real-time software is used when safety is the issue and the margin for errors is narrow. Such software is used in automotive, avionics, air traffic control, space shuttle control, medical equipment, nuclear power stations, etc. As the timeliness of those systems is critical, it needs to be assured and tested. However, real-time properties require automated tests as manual tests are untimely and imprecise. This paper reviews Testing and Test Control Notation Version 3 (TTCN-3) as a means for real-time testing and proposes extensions to enable real-time test systems in TTCN-3. Small examples demonstrate the usage of the new constructs. Real-time operating systems are analyzed and reviewed, to enable the realization of real-time test systems based on TTCN-3.