We read with great interest the Correspondence to our recent Review (Menšíková, K. et al. Endemic parkinsonism: clusters, biology and clinical features. Nat. Rev. Neurol. 19, 599–616 (2023)) by Kokubo and colleagues (Kokubo, Y., Morimoto, S. & Yoshida, M. Questioning the cycad theory of Kii ALS–PDC causation. Nat. Rev. Neurol. https://doi.org/10.1038/s41582-024-00936-0 (2024)). We are aware that Kokubo — together with the late S. Kuzuhara — systematically studied amyotrophic lateral sclerosis–parkinsonism–dementia complex (ALS–PDC) on the Kii Peninsula for more than 30 years. They authored and co-authored numerous papers about this endemic disease, some of them with one of us (R.S.). We therefore considered the comments raised by Kokubo et al. carefully, and here we respond to the questions that they have raised.