The Self-Sufficiency Project (SSP) entry effect experiment was designed to measure the effect of the future availability of an earnings supplement on the behavior of newly enrolled income assistance (IA) recipients. It used a classical randomized design. From a sample of 3,315 single parents who recently started a new period of IA, one-half were assigned to the program group and were informed that if they remained on IA for the next 12 months they would be eligible for the SSP supplement; the other half were assigned to the control group. SSP group members were asked questions and attended focus-group interviews to verify they understood the nature of the SSP supplement offer. Results indicated between one-half and three-fourths of them had relatively precise knowledge. The primary focus of the experiment was to determine whether some individuals would prolong their stay on IA to gain SSP eligibility. Analysis of the delayed exit effect suggested it was fairly small, on the order of 3 percentage points, i.e. 3 percent of all new applicants for IA. (Appendixes include additional data tables and list of 21 references.) (YLB)