The 1970 census questionnaires with instruction sheets were delivered by the U.S. Post Office to every household several days prior to "Census Day" April 1, 1970. In areas with comparatively large populations of Spanish-speaking households, a Spanish-language version of the instruction sheet was also enclosed. Households either received a short-form questionnaire which containing questions asked of 100 percent of the population (80 percent of the population received this form) or a short- and long-form survey containing questions asked of 15 and 5 percent of the population (20 percent of the population received this form).
In larger metropolitan areas and some adjacent counties (approximately 60 percent of the United States' population), households were asked to complete and return the questionnaire by mail on April 1, 1970 (resulting in an 87 percent mailback response rate), which was then reviewed by an enumerator or census clerk. Telephone or personal follow-up was made to complete or correct missing, incomplete, or inconsistent questionnaires. For the remaining 40 percent of the United States' population, instructions asked that the householder complete the form and hold it for pickup by an enumerator.