FDA-mandated post-market studies are coming. Phase IV studies are likely to be complex in design and large in scale (possibly 500,000 patients per arm), with exacting endpoints, and obligatory. The FDA appears to be abandoning a long-standing policy of negotiating post-market commitments with sponsors - and will now set mandatory objectives and timelines. There is no one-size-fits-all guidance to help a particular drug or drug class prepare for the studies. There are, however Guidance documents for ?Risk Minimization Action Plans? and ?Good Pharmacovigilance Practices and ?Pharmacoepidemiologic Assessment? and there is also the ICH E2E Guidance of Pharmacovigilance Planning. The likelihood of Data Monitoring Committees being required is also expected.