The results of the present (VIIth Complement Genetics Workshop and Conference, Mainz, May 1998) and past reference typing workshops for the terminal complement components C6, C7 and C9 are compiled and discussed both on the protein level and on the DNA level. This report also focuses on the molecular bases of expressed and silent polymorphisms and reviews the molecular bases of subtotal and complete deficiencies of these proteins and their associations with protein and DNA markers. The results of the protein typing for C6 are published in the following paper of this issue.