The evolution of the West African Examinations Council (WAEC) Senior School Certificate Examination (SSCE) and certification process is traced. The challenges posed by combining, for certification purposes, the scores from internal and external assessments of school candidates are discussed in the face of the low reliability of teachers' (internal) assessments. The previous certification procedure was based entirely on a one-shot, terminal, and external examination conducted by the WAEC. The new procedure is intended to combine advantages of continuous assessment (CASS) by teachers with those of terminal assessment (TASS). So far, there has been no official attempt to assess the validity and reliability of CASS scores submitted to the WAEC by schools in member countries. It must be assumed that disparities between schools and the qualitative difference in terms of validity and reliability between CASS and TASS scores are very wide. Examining the relationship between CASS over 3 years and TASS for 2,000 randomly selected Nigerian students for English and mathematics confirms a generally low correlation between CASS and TASS. The WAEC has chosen statistical moderation using standardization as an approach to resolving these problems. It is hoped that the experience of Nigeria in combining the two types of assessments will assist other countries as they adopt the new WAEC procedures. Six tables and two figures illustrate the discussion. (SLD)