Multimorbidity, defined as 2 or more chronic diseases, is of increasing importance for health professionals. Many factors are at play when it comes to multimorbidity, but we still know very little about how clinicians actually weigh up the different factors—medical, social, and psychological—to reach a particular course of action. Further research is therefore required to explore the ways in which clinical reasoning processes are involved in the follow up of patients suffering from multimorbidities, to highlight their potential risks of errors. A better understanding of these clinical processes will also enrich supervision of trainees and collaboration between healthcare professionals involved in primary care.