[Referees--science's watchdogs and authors best friends].

External reviewers play an important part as guardians of scientific standards and advisers to the editors of professional journals. A study of 156 reviewers in the Nordic countries showed that they make a great contribution, but differ widely from each other in their assessments of the same papers. Experienced reviewers and young referees were found to be the most critical. A trial of an evaluation check list showed that most reviewers appreciated its help.