you run nolva thru ur cycle to prevent gyno, (sometimes this doesnt work) clomid is run pct to bring your natural test production back to snuff. the reason why you take nolva thru pct is that if you just stop nolva w/ all the estrogen flowing in your body, you may have a rebound affect which means you will have a nice set of titties (exagerated).... at least this is what i understood from my research.