[WinBUGS] - Drawing Sample From Posterior

I have a working model in WinBUGS and would now like to use the model parameters to draw samples from the posterior distribution (in my case, to estimate the probability of failure). I can write code to do this externally, but can this be done in WinBUGS (or perhaps in R, using R2WinBUGS?). Any suggestions or examples would be appreciated.

Thank you.