The 19th volume deals, as did its predecessor, with current problems of tropical medicine. Both volumes are based on various international Symposia which were held in Bombay on the occasion of the 75-year Platinum Jubilee of the Haffkine Institute in the Spring of 1974. The contributions in the 19th volume are based on lectures at thetast three Symposia which dealt with Helminthiasis, Diphtheria, Pertussis, Tetanus and Cholera. The 70 articles provide the reader with an impressive cross-section of the current state of specialized knowledge on the subject and the outstanding problems. Even today, researchers from various disciplines are still confronted with numerous unsolved problems in tropical medicine, and it is to be hoped that the 18th and 19th volumes will provide a stimulus for intensified research in the area of tropical medicine. The editor further hopes that, in the future, a still more fruitful co-operation between developed and developing countries will come about. The editor owes special thanks to Dr. Rafiq Zakaria, Minister, Dr. Gaitonde, as well as Dr. Anand and Dr. Chadha, who were responsible for the organisa- tion of the Symposia on which the 19th volume is based. Thanks are also extended to Dr. A. Niif for his conscientious revision of the manuscripts and correction of the galley proofs. In addition, thanks are due to the publishers and the printers, Birkhiiuser, especially to Dr. A. Birkhiiuser, Th. Birkhauser and C. Einsele for their accurate printing and fine presentation of the volume.