In order to satisfy the needs of the many adults without a high school diploma, the New York State External High School Diploma Program was developed in 1972 as an alternative high school credentialing program for adults who have acquired skills through their life experiences and can demonstrate these skills in applied performance tests. The program's objective is to validate these skills by providing an assessment and credentialing process that is an alternative to traditional high school equivalency testing programs. This booklet provides a detailed account of the assessment procedures and materials used in the program. Following a brief description of the program in the Introduction, part 1 describes the diagnostic procedures and contains a synopsis of each of the diagnostic instruments. Part 2 describes the procedures used to assess the generalized life skills competencies. It also provides a synopsis of the original set of tasks, a brief description of the new set of tasks, and a sample task which illustrates the sorts of activities completed by candidates in the program, as well as the evaluative procedures used to assess candidate performance in each phase of the task. Part 3 describes the procedures used to determine which individualized competency should be used to assess a candidate, and gives a sample performance interview used for assessing security guard skills. (KC)