Nigel Leigh, PhD, MBBS, PhD, FRCP, FAAN, FMedSci, University of Sussex, Brighton, UK, discusses the potential clinical role of molecular biomarkers such as plasma neurofilament light (NfL) levels in amyotrophic lateral sclerosis (ALS). Various blood and cerebrospinal fluid tests as a diagnostic and monitoring tool are currently under investigation and Prof. Leigh highlights additional molecular biomarkers that may be used to assess the efficacy of therapies. This interview was conducted during the 2022 World Congress on Controversies in Neurology (CONy) meeting.