A system, based on the Apple II microcomputer, has been developed to collect cardiovascular data on-line from a non-invasive arterial pressure monitor. Off-line data are entered as far as possible, with a light pen. All information is stored on disc for subsequent analysis. A coloured trend graph can be displayed on the screen. The trend graph and all the information entered off-line can be printed out at the end of the operation to form a complete anaesthetic record.