The number of political scientists registered in the National Register of Scientific and Technical Personnel increased 25% from 1968 to 1970, from 5,176 to 6,493. This reflects a “natural” growth of perhaps 15–20%, over the two years while the remaining increase can be attributed to the greater scope of the American Political Science Association survey of political scientists in 1970. This growth in the political science section of the Register occurred despite a more restrictive definition of “professional political scientist” than had been used in 1968. Insofar as the APSA membership list can be used to gauge the completeness of the response, it would suggest that the Register is substantially complete for political science, allowing for the non-professional members of the Association and a probable residue of non-respondents. Political scientists comprise 2% of the total number of United States scientists (313,000 in 1970) in both years. More than half of National Register scientists are in three disciplines, chemistry, biology and physics.