The Survey of Income and Program Participation (SIPP) will undoubtedly become a major source of data on the economic situation of households, families and individuals in the United States. The SIPP began in October 1983 as an ongoing survey program of the Bureau of the Census with a sample of approximately 25000 “designated” housing units selected to represent the noninstitutional population of the United States. Each sample household will be interviewed once every four months for 2 1/2 years to produce sufficient data for longitudinal analyses. The reference period is the four months preceding the interview; for example, in October, the reference period is June through September. When the household is interviewed again in February, it is October through January. In February 1985 and every February thereafter, a new slightly smaller sample will be introduced. This overlapping panel design will enhance estimates of levels, and change, particularly year to year change. To facilitate field operations, each panel is divided into four approximately equal subsamples called rotation groups; one rotation group will be interviewed in a given month. Thus, one cycle or “wave” of interviewing generally takes four consecutive months. Figure 1 provides an illustration of the relationship between waves, rotation groups, interview months, and reference periods after the sample becomes fully operational in 1985. For further details of the design of the survey and plans for publication of reports see Nelson, McMillan and Kasprzyk (1984).