hi chemist told me its not good to mix proviroln while on a cycle it has very strong effect on the androgen recepter and does nt let the olther anabolloics your using not work as you would want.hes a well known chemist trainer.also masteron sholuld not give any problems unloess yolu mixx other androgens like cyp,anadrol.leave the proviron for after cycle and use with hcg if i were you i wolulod fing another drug to mix with mast. just thought this might help u. olh arimidex to me is very good drug. i woluld always choose it compare too others. josef