Born at Almora in the Kumaon Hills, about the centre of the Himalayan range, on 13 May 1857 the eldest of the ten children of Lieutenant-General Sir Campbell Claye Ross, KCB (1824-92), by his wife, Matilda Charlotte Elderton. He was sent to England in 1865, was educated at Ryde and at Springhill School near Southampton, where he showed some talent and was placed first in all England at the Oxford and Cambridge local examinations. In October 1874 he entered St Bartholomew's Hospital and acted as dresser to Sir William Savory, but held no resident appointment. He was unqualified house surgeon at Shrewsbury Infirmary for six months in 1877-78 and ship's surgeon in the Alsatia, Anchor line, in 1879. He was gazetted surgeon IMS on 2 April 1881, having been posted to the Madras Presidency. He served at various stations until June 1888 when he came to Europe, took a course of bacteriology under Emanuel Klein, and returned to Bangalore as staff surgeon in 1889. He then began his life's work in connexion with malaria. Alphonse Laveran, a French Army surgeon, working in Algeria from 1878-80 had identified a living cause for the disease, as a microscopic protozoal organism which had an asexual phase coincident with the acute stage of the fever and a sexual phase the fate of which was unknown. Patrick Manson had discovered that mosquitoes ingested filariae with the blood of patients suffering from elephantiasis, and suggested to Ross that malaria parasites might pass in the same way or might infect healthy persons who swallowed, in drinking water, mosquitoes or even the germs themselves which had been excreted by the insects. Ross to elucidate the problem made many dissections of mosquitoes and distinguished Culex the pot-breeding mosquito and Stegomyia. Continuing his work he discovered the malaria plasmodium in the stomach of Anopheles, the pool-breeding mosquito, on 20 August 1897 whilst working in the hospital at Begumpett near Ootacamund, and in July 1898 he demonstrated it in the ducts and salivary glands of the insect. Working with birds, as Laveran had already done, Ross then extended his results to humans. He proved that the malaria organism was not passed directly from victim to victim by the mosquito, but that it underwent regular changes in its life history within the insect, which did not become infective to a new host for twelve days in the case of human malaria. Ross left the Indian Medical Service in 1899 and after a journey to West Africa was appointed professor of tropical medicine in University College, Liverpool. In 1901 he lectured in the United States, in 1907 went to study malaria in Mauritius, and in 1913 for the same purpose to Cyprus. During the war he served in Alexandria and in 1917 was appointed consultant on malaria with the rank of lieutenant-colonel in the RAMC(T). He resigned his post at the University of Liverpool, came to London, was made consultant in malaria to the Ministry of Pensions, and founded at Putney Heath the Ross Institute and Hospital for Tropical Diseases. The Institute was opened by HRH the Prince of Wales in 1926. Ross was also editor of *Science Progress* from 1913 till his death. At no time a rich man, Ross sold the papers connected with his discoveries in malaria. They were bought by Lady Houston for £2,000 and were presented by her to the Ross Institute, where they are now preserved. In 1929 a "Ross Award Fund" was collected by scientific friends which amounted to £15,513. He married in 1889 Rosa (d 1931), daughter of A B Bloxham, a lady of much talent who contributed greatly to the success of her husband's work. He died on 16 September 1932. Many honours came to Ross, but somewhat late in life. He was awarded the Parkes' memorial gold medal at Netley on 20 March 1895; the silver medal of the Society of Arts in 1901; the Cameron prize, Edinburgh University, in 1902; the Nobel prize in medicine in 1902; the Barclay bronze medal of the Asiatic Society, Bengal, in 1903; the Royal gold medal of the Royal Society in 1909; besides other distinctions conferred by foreign governments and societies. Ross's nature was complex. Coming of a highly artistic family, both in music and water-colour sketching, he added some skill in mathematics and the dogged perseverance, amounting to genius, which enabled him to unravel the life history of the malarial plasmodium. He failed to appreciate, however, that great discoveries need time to be appreciated, and his life was embittered by what he considered to be deliberate official neglect of his work. His poetry was of a high order of merit, more especially the privately printed *In Exile*, a suite of verses written 1890-97. Publications: *Instructions for the prevention of malarial fever*. University Press, Liverpool, 1899; 6th edition, 1901. *Malarial fever, its cause, prevention, and treatment*. University Press, Liverpool, 1902; translated into German, 1904 and into modern Greek, 1906. *Mosquito brigades and how to organise them*. London, 1902 (*Lpool Sch Trop Med*, Memoir 2). He wrote several mathematical papers, in addition to his purely scientific papers, which appeared chiefly in the *British Medical Journal* and the *Indian Medical Gazette*, and the poems and romances.