Abstract: The invention relates to methods and apparatus for checking compliance with disulfiram prescription regime. The apparatus includes a device for monitoring, on a regular basis the levels of volatiles in the users breath and a comparator for comparing the test results with anticipated results and producing a non-compliance output when a non-compliance event is detected. The apparatus includes an indicator for providing an indication that carbon disulphide is present in the measured volatiles. The detector of the apparatus detects, at least acetone and carbon disulphide.