Thanks Krishna! You are correct, but even when I manually add m<-17 just after x I still get the same error? Uniroot falls over when it tries to take in the argument MLEobj=fit, thus I think the error is occurring before LamOpt() gets called by uniroot(). Which is why the error you mentioned didn't show up before and thus unfortunately the original error still persists. Baz -- View this message in context: http://r.789695.n4.nabble.com/Unable-to-pass-Object-Arguments-to-UniRoot-tp4710938p4710943.html Sent from the R help mailing list archive at Nabble.com.