SYNOPSIS Three trials of E. urophylla and E. alba seedlots were established, one in the semi-temperate eastern Transvaal and two in subtropical Zululand, during 1973 and 1974. The trials consisted of imported seed-lots of both species and South African and Brazilian collections of E. urophylla. Although the trial in the eastern Transvaal suffered frost damage, both the volume and the wood mass growth of E. urophylla were better there than in Zululand. Volume production of E. urophylla was less than that of either E. grandis or E. saligna of the same age, but because of the higher wood density of E. urophylla the wood mass production of this species was better than that of E. saligna and equal to or slightly better than that of ordinary E. grandis. The stem form of most E. urophylla seedlots was very good. Within the species, two types of E. urophylla were distinguishable, the smooth-barked and the rough-barked. Although the two types did not differ much in volume production in Zululand, in the eastern Transvaal the rough-barked seedlots were superior. The smooth-barked seedlots had a higher basic wood density than the rough-barked types, making them superior wood mass producers in Zululand. In the eastern Transvaal the rough-barked seedlots, because of their very good volume production, were the best wood mass producers despite their lower basic wood density. Eucalyptus urophylla has shown very high potential as a producer of mining timber and pulpwood and there are indications that it could be a good sawtimber species. Eucalyptus alba seedlots showed poor to fair growth and poor to very poor stem form. This species has no potential for use in South Africa.