As part of a U.S. Bureau of Mines program to develop a more continuous titanium metal process that exploits domestic resources, a study was made of the kinetics of hydrofluoric acid (hf) leaching of New York rock ilmenite. The effects of leach temperature, hf concentration, and particle size on leach rate were investigated. The data fit a shrinking core model with the rate controlled by the chemical reaction step. The rate of reaction is related to temperature by the arrhenius relationship, with the activation energy being 52.6 Kj/mol for titanium and 48.4 Kj/mol for iron. The rate is linearly dependent on the hf concentration and inversely proportional to the average starting diameter of the particle. Generalized rate expressions were developed for titanium and iron. Using 19.33 M hf at 45 deg c, 99 pct of the titanium and 100 pct of the iron in New York rock ilmenite were leached in 40 min.