The paper describes the techniques and data adopted for the construction of a new series of estimates of the stock of education in 85 countries over 28 years (1960-87). The series are built from enrollment data using the perpetual inventory method, adjusted for mortality. Estimates are corrected for grade repetition among school-goers and country-specific drop-out rates for primary and secondary students. Enrollment data series used start as far back as 1930 for most countries, and even earlier for others. This reduces the need for backward extrapolation of enrollments to provide the initial estimates of the investment inventory.