I would like to put traces on the methods for an SV3 generic and trace() doesn't seem to work. E.g., > median(1:10) [1] 5.5 > trace(median.default) > median(1:10) # expect "Tracing median.default ..." [1] 5.5 I can tell that median.default is getting called, since a trace on sort() shows it in the traceback: > trace(sort,Quote(cat(deparse(sys.calls()),sep="\n"))) Tracing function "sort" in package "base" [1] "sort" > median(1:10) Tracing sort(x, partial = half + 0L:1L) on entry list(median(1:10), median.default(1:10), sort(x, partial = half + 0L:1L), .doTrace(cat(deparse( sys.calls()), sep = "\n"), "on entry"), eval.parent(exprObj), eval(expr,p), eval(expr, envir, enclos)) [1] 5.5 Is there a recommended way to do this? (I'd like to put a trace on all methods of a SV3 generic to see which get called in various situations.) This was in R 2.8.1 on Windows but I see the same results in several versions of R. Bill Dunlap TIBCO Software Inc - Spotfire Division wdunlap tibco.com