After 1950, following pontifical approvals, single and married people of all walks of life were able to join Opus Dei. The celibate members now included the aggregates in addition to the numeraries. In this article, which is a prelude to a more extensive study, we will examine, in the first place, the itinerary that led to the approval of the idea of the associate, and in the second place, we will describe the process through which the first four male associates were incorporated into Opus Dei between March 1950 and February 1951.