The Hough transform is a projection-based transform which can be used to detect shapes in images. One of the disadvantages of the transform is its requirement for large amounts of computing power. Parallel machines have given programmers the potential for incredible computing power. To obtain maximum performance from parallel machines, parallel algorithms should be designed to reflect the architecture of the parallel machine. The work reported in this paper compares the performance obtained in running several parallel versions of the Hough transform on a Fujitsu AP1000 distributed memory multiprocessor. ᭧ 1999 Published by Elsevier Science B.V.