In 2007, IIASA and the Vienna Institute of Demography of the Austrian Academy of Sciences (VID) released a database reconstructing detailed information on levels of educational attainment by age (in five-year age groups from 15 to 65+ years), sex, and for every five years between 1970 and 2000 for 120 countries (see Lutz et al. 2007). This database was created in two steps. The reconstruction methodology was applied for the first time and generated what is called the Beta version of the database (unpublished). This paper presents the validation procedure that was implemented to check the plausibility of the Beta version against scattered real data from different sources, mostly from the UNESCO collection of levels of educational attainment. The verification was done by using two main indicators where a comparison was possible: Proportion of the population with no education (E1) and proportion with a tertiary education (E4). The validation procedure was a crucial factor in arriving at the present version of the database (called version 1.0). This paper also presents the results of the validation of the published version against real data, and highlights the need for the harmonization of education data to facilitate comparison over time and space.