The Application Response Measurement (ARM) API defines function calls which can be used to instrument an application or other software for transaction monitoring. It provides a way to monitor business transactions, by embedding simple cells in the software which can be captured by an agent supporting the ARM API. The calls are used to capture data that allows software to be monitored for availability, service levels, and capacity. The API can be used by programmers who want to collect performance information by instrumenting the business logic of their applications, or on other software in their domain, where there is ready access to the source code of the business logic on the systems involved. Collection of ARM-related data from the software components which surround the business logic may be possible using this ARM API. Applications (and other components) must normally be running within the reach of the enterprise management domain in order to allow for collection and presentation of performance data from agents. This Issue of the ARM Technical Specification defines a Java API, suitable for instrumenting Java applications and applets.