During the year April 1921–April 1922 I examined the stools of 1034 men from the dysentery ward of the District Hospital, Kuala Lumpur, in the Federated Malay States. In this hospital the patients are for the most part indigent Chinese and Tamils of the coolie class, who have resided in Malaya for a length of time varying from a few weeks to a number of years, sometimes all their lives. From the way in which these people live, from the intimate mixture of so many different nationalities, and from their often extensive migrations, one might be led to expect that their intestinal fauna would be abundant both in variety of species and in incidence of infection. This expectation is not realised in the following results. Indeed, the figures for some of the non-pathogenic protozoa are not as high as some which have been obtained for healthy Englishmen who have never left England (cf. Matthews and Malins Smith, 1919). Nearly all the patients in this series were suffering, or had recently suffered, from active dysentery at the time when the examinations were made: and in some cases the flushing out of the intestine from this cause probably reduced the intestinal protozoa to such small numbers that none could be found when specimens of the stools were examined. In many cases, also, protozoa have certainly been overlooked in the masses of pus and other cells present in a very large proportion of the stools examined. Had it been possible to examine a series of cases without intestinal derangements involving diarrhoea from the same population, some opinion might have been formed as to the actual effect of these two factors on the results obtained. And until some such figures are available for comparison it cannot be said that the scarcity of some of the intestinal protozoa found in these cases has any special significance.