Background: Certifying physicians play a key role in the management of sickness absence and are often provided with guidelines. Some of these guidelines contain statements on expected sickness absence duration, according to diagnosis. We were interested in exploring the evidence base of these statements. Methods: We identified guidelines through a survey of EUMASS members and a literature search of the Internet and PubMed. We extracted the statements and methods from the guidelines. We compared: diagnoses that were addressed, expected durations and development processes followed. Next, we presented our findings to the developers, to afford them an opportunity to comment and/or correct any misinterpretations. Results: We identified 4 guidelines from social insurance institutions (France, Serbia, Spain and Sweden) and 4 guidelines from private organisations (1 Netherlands, 3 US). Guidelines addressed between 63 and some 63000 health conditions (ICD 10 codes). Health conditions overlapped among guidelines. Direct comparison is hampered by differences in coding (ICD 9 or 10) and level of aggregation (three or four digit, clustering of diseases and treatment situations). Expectations about duration are defined as minimum, maximum, and optimum or mean or median and percentile distribution, stratified to age and work requirements. In a sample of 5 diagnoses we found overlap in expected duration but also differences. Guidelines are developed differently, pragmatic expert consensus being used most, supplemented with data on sickness absence from different registers, other guidelines and non-systematic literature reviews. The effectiveness of these guidelines has not yet been formally evaluated. Conclusions: Expectations about duration of sickness absence by diagnosis are expressed in several guidelines. The expectations are difficult to compare, their evidence base is unclear and their effectiveness needs to be established.