This paper explores the meaning of chronicity and terminality in motor neurone disease (MND), also known as amyotrophic lateral sclerosis (ALS). There is no known cause or cure for MND, and expected survival is 2–5 years, but several interventions may improve or prolong life. This study draws on qualitative interview data with health professionals in hospitals and primary care, and family carers, in Norway. The actors emphasised chronic and terminal aspects in subtly different ways along the entire illness trajectory, also when recounting the trajectory in retrospect. As a consequence of improved health services and medical technology the distinction between chronicity and terminality has become more vague and sometimes ambiguous. We suggest the concept unstable terminality to describe this ambiguity. While MND is a fatal diagnosis; it may be contested, as contingencies and interventions create an indefinite time scope. The instability creates challenges for primary care which is dependent on prognostic information to organise their effort; hospitals tackle the instability by pre-scheduled consultations allowing for avoidance of an explicit prognosis. Some carers experienced what we understand as a disruption within the disruption, living with chronic and terminal illness simultaneously, which made the limbo phase more challenging to overcome.