An introduction describes the study and discusses sampling, weighting, data collection procedures, pretesting, file structure, information processing, and codebook information. Survey objectives were to develop detailed information about the victims and consequences of crime, to estimate the numbers and types of crimes not reported to police, and to provide uniform measures of selected types of crimes permitting reliable comparisons over time and between areas. The offenses selected were rape, robbery, assault, burglary, larceny, and motor vehicle theft. The NCS used two distinct samples: a national sample and a cities sample. The national sample consisted of approximately 72,000 sample units selected in a stratified multistage cluster. The cities sample consisted of 26 central cities, from which data were collected in five surveys between 1972 and 1975, each involving a similar sampling procedure. About 12,000 sample households were selected in each of the 26 cities, with approximately 10,000 interviews conducted in each city. The NCS data come as OSIRIS data sets, each composed of two components: a machine-readable dictionary for use in conjunction with the OSIRIS software package and a separate data file.