The proposed rules published by the FDA in the Federal Register in Feb. 2019 had the biggest impact on sunscreen formulations since the publication of the first tentative monograph in August1978.In this presentation, the MUsT (Maximal Usage Trial) study conducted by the FDA that led to the proposed changes will be discussed as well as the impact of those changes on future formulations.In addition, an in-depth review of formulation strategies with zinc and titanium oxides will be presented.Methodologies used to screen various types of inorganic sunscreens such as zeta potential, contact angle, particle size anal., SEM microscopy and Hegman gauge will be presented and compared.The effect of particle size on SPF and skin whitening will be discussed.Differences between formulating inorganic sunscreens in O/W and W/O emulsions and their impact on water resistance and formulation stability will be reviewed.The addition of polymers and SPF boosters to increase SPF and water resistance will be presented along with some in vivo SPF testing data.The work presented will enable formulators to get a head-start to adapt their formulations to the guidelines set forth by the FDA and prepare them to formulate efficiently with inorganic sunscreens.