He trained at the Institute of Neurology, Queen Square, as a Nuffield Research Fellow London working with Lord Roger Bannister and Dr Ross Russell.

Peiris refurbished and equipped the former staff tea room into the first neurology intensive care unit.

[5] Peiris was responsible for many of the donations for the construction of the Institute of Neurology and also collaborated with the technical committee headed by Navin Gooneratne of Design Consortium and Mohan Coomaraswamy of Project Management services on a weekly basis for three years.

The public funds collected for the construction was managed and distributed by the All Ceylon Buddhist Congress (ACBC), with the donation for the ground floor coming from Mrs Milina Sumathipala.

The hospital welfare service, which is a branch of the ACBC (at the time headed by Ven Vipassi Thero) played a supportive role.

The original descriptions were on Non familial juvenile distal spinal muscular atrophy of upper extremity, a delayed onset Cerebellar syndrome complicating Falciparum Malaria, Transient Emboligenic Aortoarteritis[7] – a noteworthy entity in strokes in the young as commented by the Editor of the Archives of Neurology, July 1978.

MRCP – Neurology for PACES[14] is authored by him with physician daughter, Dr Natasha Peiris, and was released in UK.

The Dr J B Peiris Oration is organised annually by Association of Sri Lankan Neurologists (ASN), in recognition of the services he has rendered.

Speaking at the inaugural oration, Dr Ranjani Gamage, Consultant Neurologist at NHSL, summoned up Peiris's lifetime of contributions to humanity stating that "What we have done for ourselves alone, dies with us, what we have done for others and the world remains and is immortal.

[19] They have a daughter, Natasha, who is a Consultant Physician,[20] and son, Shanaka Jayanath, a Senior Economist with the International monetary Fund in Washington, D.C. (and now the IMF Resident Representative in Manila).