Billy is on the right track....Nolvadex (Tamoxifen Citrate) is a prescription estrogen blocker (6-oxo proposes to do the same thing). These are best to take post cycle in the event that the suppressed test production leads to elevated estrogen levels and unsightly sides such as gyno. During an AAS cycle you may want to take something like arimidex (an aromatase inhibitor) to help prevent the conversion to estrogen...but with M1T, this is not a factor. The only problem with M1T is the post cycle suppression of natural test production. That being said...I only took 6-oxo for pct and I did not experience any type of gyno. Then again, I didn't run any tests, so I don't know if the 6-oxo was that effective, or if it was just that my estro levels didn't increase that high.