The jaundice, which occurred among coal- miners working in certain collieries in East Lothian, was diagnosed clinically by Professor G. Lovell Gulland, and proved bacteriologically by the writer, to be of spirochaetal origin (January 1924). Wild rats and field mice from. the infected mining area were incriminated as carriers of the causal organism in Scotland for the first time (January 1924):.. The diagnosis in 22 cases of the disease was based on the combined clinical, laboratory and experimental observations described. In 22, jaundice was a feature. In 1T7, haemorrhage, mainly epistaxis, occurred. In 17, spïrochaetes were found in the urine. Spirochaetal jaundice was produced in two guinea -pigs inoculated with urine from two of the patients, and in eight "spotted" lung haemorrhages were the only signs of infection. The figure for the death rate among coal -miners approximates very closely that reported by Inada in Japan, viz. - 50.6 per cent. The establishment of a diagnosis by means of ,bacteriological procedure was attempted. Blood examination for the spirochaete proved negative in all cases, as did guinea pig inoculations with suspected 1. blood. The urinary examination for the .presence of the spirochaete proved more helpful, but the organism; was never observed under the dark- ground microscope or in stained films in typical form. The results, of guinea pig inoculation with suspected urine containing spirochaetes were very uncertain. The writer is of the opinion, however, that in cases of jaundice in which the clinical signs point to the spirochaetal form,and in the urine of which granular spirochaetes are found, the chain of evidence is strong enough to justify the diagnosis of spirochaetal jaundice. As an aid in diagnosis, serological methods were applied in several cases but without very definite results. No agglutination of the spirochaete was observed when tested with the blood serum of four patients during convalescence, but a lytic action of the serum on the spirochaete was demonstrated in a few instances. The serological aspect of human infection was not studied to any extent owing to the difficulty of obtaining material for this purpose. The writer was instrumental in effecting the pr-eparration of a specific anti-serum from the local strain of the organism. The number of human cases in which it has been used, is too few, however, to state an opinion regarding its efficacy. The chief prophylactic measure is agreed to be rat extermination as far as possible,- and moreover in infected coal-mines, improved drainage7as Inada found that this measure was responsible for a decrease in the incidence of the disease in certain wet mines in Japan. The usual precautions applied to other infectious diseases should also be put into force. Active immunization was established by the Japanese who administered spirochaetal vaccines with very satisfactory results.