YELLOW FEVER seems to be something of past, something that no longer inspires special interest from sanitarian, an enemy already defeated, something out of fashion. After victorious campaigns carried on in Cuba, Panama, Brazil, etc., it seems no longer to demand special attention. However, for one coming from Guayaquil, port that during three quarters of a century suffered from that calamity, and whose ill fame kept travelers away, fearing to approach its shores, and retarded commerce with other nations, it seems natural to speak once more of place for so many years infected, but to-day free, due to simple but efficient resources of modem hygiene. The history of main features of this successful campaign, and present condition of what was formerly called the Pest Hole of Pacific Coast, may be of value to those interested in presentday sanitary problems. Guayaquil, with a population of 100,000 inhabitants and an area of five square kilometers, is located on western bank of Guayas River, 45 kilometers from sea and five meters above sea level. Its temperature fluctuates from 200 C. minimum in cool season, to a maximum of 340 C. during hot season. From June to December climate is dry, temperate, and pleasant. During rest of year, rainy season, temperature reaches maximum point, mosquitoes appear and multiply rapidly and atmosphere, loaded with humidity, is favorable for development of germs and epidemics. The streets, after repeated destructive fires, were widened and straightened-the principal ones paved with asphalt. However, in suburbs streets, patios, and ground underneath houses are totally submerged during rainy season. Two factors of great hygienic importance for a locality are very deficient in Guayaquil-water supply, drainage and sewerage system. The present water supply comes from brooks in mountains, about 90 kilometers from city. The pipe line parallels line of Guayaquil and Quito Railroad to bank of Guayas River, where it is carried under river to city. Its purity is more or less satisfactory, as it is found to contain only a moderate number of B. coli, probably not of human origin. But amount of water supplied to city during twenty-four hours is very small (2,000,000 liters or 20 liters per capita) ; it should and will be increased at any cost to reach at least an amount .five times larger. This insufficiency of volume of potable water, as well as fact that it runs through mains only two or three hours a day, causes people to store water in tanks, cisterns, barrels, etc., thus affording firstclass breeding-places for mosquito. Toward southwestern part of Guayaquil there are large marshes which are periodically flooded by flow of Estero Salado (a bayou running from gulf). This water fortunately is brackish enough to prevent development of Aedes cabopus. It is probable that yellow fever existed in Ecuador long before 1842, and early historians tell of occurrence of fevers, violent and fatal, that attacked pirate crews during their frequent