A brown strain of Kappaphycus alvarezii from the Philippines produced tetraspores in the summer and autumn (December 1995 to May 1996) in cultivation experiments in the sea at Ubatuba, São Paulo State, Brazil. In vitro tetraspore release and germination experiments showed a mass mortality two to four days after release. Only 20 plants derived from tetraspores were grown successfully for over a year in the laboratory. Large differences in morphology, colour, size and growth rates were observed amongst these plants. The individual plants differed from one another in one or more characteristic. Differences appeared in the early developmental stages and persisted through time. After ten months, the plants that grew best in laboratory culture were transferred into the sea, but the others remained very small (3 to 5 mm), even after two years. In the sea, the plants also showed individual differences in their ability to survive and grow. These results emphasise the potential of the tetraspore progeny for strain selection in K. alvarezii. The results also suggest that the tetrasporophyte used in these studies is of hybrid origin.