Systematic observations were made on reindeer feeding behaviour during 1973–74, and seven phanerogams and three bryophytes were selected for sampling during the following year. Material of the principal plant species in the main communities at a study site was harvested and analysed for crude fibre, holocellulose, nitrogen, phosphorus, potassium, calcium, magnesium and ash. Contrary to expectation, crude fibre data show an early season peak in most species, whereas holocellulose data are more variable. Seasonal trends in mineral elements were similar to those found in nearby ungrazed vegetation, and to those in northern temperate species, although absolute values were often higher than in the latter. Data from material collected within and outside a deer-proof exclosure suggest some degree of nutrient input by the animals in the grazed situation, and nutrient enrichment was also apparent at a site colonized by white-chinned petrels. Differences in nutrient content occurred in species collected from both a freely-drained, exposed site and a wetter, more sheltered area, but these were not consistent. Data are considered in relation to the diet of South Georgia reindeer as determined by rumen content analysis, and are compared with those of forage species of northern reindeer and caribou.