Background: Previous studies have examined manageability and meaningfulness in amyotrophic lateral sclerosis (ALS), but there is a lack of studies examining the comprehensibility of ALS among patients and their spouses. Aim: This qualitative retrospective study aimed to illuminate patients' and spouses' experiences of comprehensibility in ALS from a long-term perspective, when symptoms appeared before diagnosis, and when the diagnosis was given and in life after diagnosis. Methods: Individual semi-structured interviews with 14 patients and 13 spouses were performed. The transcribed interviews were subjected to qualitative content analysis. Findings: Through the whole disease process, patients and spouses feared the unknown regardless of whether they comprehended the disease or not. They described that they before diagnosis felt uncertainty. It was problematic to comprehend what was wrong and what the deterioration implied. At the diagnosis, they described feelings of losing their foothold. Long-term after diagnosis, they still lived in fear and looked for reasons why they were afflicted. Conclusions: Findings of similar experiences in comprehensibility between patients and spouses strengthen the importance of support and information to both parties. Since they hovered between comprehensibility and incomprehensibility during the whole disease process, it is important that their questions, fears and worries are met, from the first visit at hospital and through the whole process. Multiprofessional teams, such as ALS teams and palliative teams can from a holistic perspective increase the possibility of meeting their needs in their unique situation.