All persons engaged in or able to engage in work related to the creation, development, spreading and applying science and technology.

International methodological recommendations for the measurement of this population size as well as the methods of analysis of its structure and changes are included in the Manual on the Measurement of Human Resources devoted to S&T (the "Canberra Manual") developed jointly by the OECD and Eurostat. Human resources in science and technology are defined as persons fulfilling at least one of the following conditions:
- successfully completed at tertiary level in a Science and Technology (S&T) field or study (ISCED-97 version levels 5a, 5b or 6);
OR/AND
- not formally qualified as above but employed in an S&T occupation where the above qualifications are normally required (ISCO COM codes 2 or 3).
Measurement and analysis of human resources for science and technology (HRST) are conducted according to two internationally harmonised standards:
- The International Standard Classification of Education — ISCED — gives the level of formal education achievement;
- The International Standard Classification of Occupation — ISCO — details the type of occupation. Until 2010, according to the ISCO-88, and from 2011 on - according to ISCO-08.