Screening of applicants and selection of interns for surgical residency programs continue to rely heavily on letters of recommendation from surgical faculty. To define important aspects of letters useful for screening and selection, letters written on behalf of housestaff with known performance and those of new applicants were circulated to a sample of 120 academic surgeons. Eighty letters, written on behalf of 42 students, were divided into 10 groups of 8; each group was sent to 12 individuals. Half of the letters were "open" (full letter-head and signature), and half were "text only" (i.e., no identification). Candidate names were omitted. Each faculty reviewer was asked to rank the candidate represented by each letter, for their program, on a scale of 1 to 5, and indicate key negative or positive phrases on individual letters. Reviewers were also asked to indicate the importance they generally ascribe in evaluating such letters to the school of origin, academic rank of the letter writer, personalization (of letter to reader), formal vs informal reference to the candidate, and mention of interest in specialty training. A response rate of 60% was obtained. Faculty reviewers stated explicitly that school of origin, personalization of the letter, and the academic rank of the writer are important factors influencing their ranking of candidate letters. The scores they gave to "open" and "text only" letters, however, do not differ significantly (P > 0.05). Letters were scored similarly, indicating that school of origin or writer may not be as critical as implied or believed.(ABSTRACT TRUNCATED AT 250 WORDS)