### What you need to know Patients diagnosed with a serious illness often ask doctors about prognosis as a way into talking about what life might be like in the future.12 Illness trajectories can offer conceptual maps of archetypical patient journeys in the final years and months of life. Trajectories have been used clinically for nearly 20 years to aid timely identification and assessment of people for a palliative care approach34 and, more recently, in population based studies of access to palliative care.56 Advance care planning involves making plans with the patient and family when there is a risk of deterioration so that future care is in line with what matters to them and informed by clinical advice. Person centred conversations are central to meaningful advance care planning, and discussing a possible future illness trajectory can be a useful part of the process.78 This article offers an overview of illness trajectories that may be relevant for people with any progressive illnes