Authorship is important. As the International Committee of Medical Journal Editors (ICMJE) guidelines¹ state up front, “It confers credit and has important academic, social, and financial implications. Authorship also implies responsibility and accountability for published work.” Those guidelines clearly delineate the 4 criteria that must be met to qualify for authorship: (1) substantial contribution to the work, (2) drafting or revising the paper, (3) final approval of the paper, and (4) accountability for the work. Ethical behavior pertaining to studies and their publication is extensively addressed in the ISPOR Code of Ethics.² And yet seemingly difficult issues remain, as evidenced by our collective experience as authors, reviewers, and colleagues of those seeking publication. Two issues surface repeatedly that are not discussed in detail in the guidelines: Are their acceptable grounds for excluding from authorship any who meet the 4 criteria (or for including some who do not)? What is the appropriate author order?