Mrs. McTavish is a 25-year old patient whose Papanicolaou (Pap) test results have come back from the laboratory. The smear is described as satisfactory for evaluation; however, it is noted that an inadequate number of endocervical cells were present in the sample. The results of the patient's past Pap tests have been satisfactory for evaluation and negative for abnormality. She is otherwise well. Her physical examination, including pelvic examination, showed nothing unusual. R ates of cervical cancer have been declining in Canada since the implementation of the Papanicolaou (Pap) smear, with reduction in both incidence (from 11.1 per 100 000 in 1970-1972 to 5.2 per 100 000 in [1994][1995][1996] and mortality (7.9 per 100 000 in 1953-1955 to 1.9 per 100 000 in [1995][1996][1997].1 Further improvements will depend on the continuance of screening for cervical cancer and the effectiveness of screening tools. The Bethesda System -the conventional system for reporting cervical cytologic diagnoses -provides feedback about specimen adequacy using the categories "satisfactory" or "unsatisfactory."2 Primary health care providers may receive Pap test results that are identified as satisfactory but accompanied by a note that indicates a sample from the transformation zone is lacking. Some provincial and national guidelines are unclear about how clinicians should respond to this type of report. Because of this uncertainty, we sought to review the current evidence on the topic. How should a care provider proceed with screening when faced with an otherwise satisfactory Pap smear that lacks sampling from the transformation zone? If physicians continue with regular screening intervals without special attention to the lack of endocervical cells, are cervical abnormalities being missed? Literature reviewWe searched MEDLINE from 1975 to the end of July 2010 using the following combination of keywords and subject headings: "unsatisfactory Pap smear," "endocervical component," "endocervical status," "endocervical cells and Pap smear," "Pap smear and quality" and "abnormal Pap smear." Bibliographies from the identified articles were manually searched. Summary sites such as Towards Optimal Practice (Alberta) and Cancer Care Manitoba were also reviewed in July 2010. We identified 462 citations, and reviewed 53 full-text articles. Papers were excluded if they were written in a language other than English, if they did not discuss the topic of Pap smear quality and presence or absence of endocervical cells, and if there were insufficient data to draw conclusions. Twenty-four articles were included in our review and are summarized in Appendix 1 (available at www .cmaj .ca/cgi /content /full /cmaj .101156 /DC1).The level of evidence was determined by the hierarchy developed by the Canadian Task Force on the Periodic Health Examination, 3 according to which the highest level of evidence (Level I) derives from at least one randomized controlled trial, and the lowest level derives from the opinion of experts (Level III). The evidence identified...