The role of document examiners is to consider differences as well as similarities and to give weight to both. However, the evaluation of the significance of differences and of the nature and amount of evidence necessary to support an elimination has received little attention in the textbooks, training, and informal conversations of document examiners. Assigning weight to similarities is second nature to experienced document examiners. Assigning weight to differences is often much more difficult; several factors need consideration. First, the difference must be repeated and/or must be in combination with other differences, some of which similarly must be repeated. Second, differences in features that are unusual carry more weight than those that are not. Third, the document examiner must judge the naturalness in the writing. Finally, the document examiner must rule out permanent or transitory factors such as disguise, change in habit, multiple styles, accidentals, and normal variation. This final judgment is often the most difficult to make. If sound reasoning is used in the evaluation process, it should not be difficult to determine at which point differences should be called significant. A difference should not be called significant until it can be determined to be probably fundamental to the structure of the writing. Document examiners should assign proper weight to both similarities and differences to justify both identifications and eliminations; they should also think for themselves and not accept as fact everything they receive from textbooks or trainers. 39 reference notes and 3 additional references