Formally, the BCLC knows two types of participants:

Initially, the Breast Cancer Linkage Consortium operated only through meetings with a workshop format and consisted only of researchers sharing information on linkage analysis in breast cancer families and on LOH in breast tumors (see history of the BCLC). Soon after BRCA1 was identified, interest in the BCLC grew much stronger, because many centers worldwide became involved in mutation testing. As a result, more groups contributed data to BCLC studies, but there were also many who only wished to attend the annual BCLC meetings, in order to remain informed about the latest progress. These meetings therefore grew much bigger, loosing some of the informal character it had in the early days.

In addition, since 1993, a number of centers in Europe received funding from the European Commission for concertation of their activities within the BCLC. Thus the secretariat of the BCLC now holds two databases with addresses: one for the contractors on the European concerted action on hereditary breast cancer, and one with all others, i.e., contributors and attendees of the general meetings.