The materials used were healthy young sporophytes of L. japonica and U. pinnatifida collected from Qingdao. The middle parts of the blade and the rhizoids of L. japonica were cut into 1 × l cm² and 1 × 0.3 cm² pieces separately. The blade and the rhizoids of U. pinnatifida were cut the same way except that the coastae were cut as new material (1 × 0.3 cm², or l cm long and 0.8 cm diameter). A Biolistic PDS-1000/He Particle Delivery System (Bio-Rad Company, U.S.A.) was used to deliver DNA into intact algal cells. Gold microprojectiles were coated with plasmid pBI221 (CaMV35S promoter-GUS gene-nos ter). Control tissues were bombarded with gold microprojectiles without DNA. After two days' culture in MS medium, tissues were stained for histochemical assay. Negative results were obtained for GUS activity in all control tissues. No GUS background reaction was found inside brown algal cells (Plate I:1, I:2) and blue spots were found scattered inside the rhizoids of L. japonica (Plate I:3, a cut-open rhizoid) and beneath the surface of costa of U. pinnatifida (Plate I:4). These findings indicate that particle bombardment can be used to deliver DNA into many intact algal cells simultaneously and that the foreign gene introduced by this proccess can be transiently expressed using CaMV35S promoter. An appropriate selection marker can be used to select transgenic seaweeds.