Muntjacs (Muntiacus muntjak malabaricus) were studied in the Wilpattu National Park in NW Sri Lanka from Sept. 1972 to OCt. 1973. Of 1005 muntjacs that were identified to age and sex, 64.5% were solitary, 30.8% were in pairs, and 4.7% were in groups of 3 or 4. No groups were larger than 4. The most common pairs were an adult male with an adult female (79 cases) or a female with one offspring (50 cases). The overall adult sex-ratio, derived from sightings was 91 males to 100 females. The population density was estimated at 2.5 adults per km2 during the drought. Reproduction was apparently spread over the whole year even though males exhibited a definite cycle in their antler growth, with most antlers being shed from June to Aug. Out of 57 males identified in a given area, 30 (53%) had some injuries that probably resulted from intraspecific combats. Muntjacs fed on tender leaves and fruits on the 27 cases where the food eaten was identified. Animals were seen most often in the forest, they came out in the open only to drink and always for short period. From the temporal distribution of alarm barking and visits at the water holes the muntjacs appared to be active mostly right after sunrise and also just before sunset. The main attributes of the life-form to which muntjacs belong, that of a small-solitary-forest-ruminant, are presented and discussed in terms of their adaptedness and interrelationships.