Designing parallel programs to maximise the utilisation of the processing power of a multiprocessor machine requires a series of performance analysis and tuning. This paper describes a performance tuning tool for message-passing parallel programs. The tool uses a logical clock approach to instrument the program for collecting performance data. Combining the advantages of relational databases and three-dimensional spreadsheets to organise the performance data, the tool provides visual assistance for analysing the program performance. Various graphical displays which help the user to fine-tune the performance of message-passing programs are discussed.