Sorry about using this mailing list for other than what it was intended, but I think you are best qualified to answer my question. Is it true that the state of the art in pausing garbage collection algorithms is the one by Douglas Clark, "An Efficient List-Moving Algorithm Using Constant Workspace", in CACM, June 1976, Vol. 19, No. 6, pp. 352-5? I know that T uses this algorithm. John