The effects of different concentrations (10-5, 5 x 10-5 and 10-4 M) of copper bromide on spore germination, growth and ultrastructure were investigated in Polypodium cambricum L. gametophytes. The inhibitory effect of Cu was observed in spores cultured on medium supplemented with 10-4 M CuBr2: germination occurred about 40 days after sowing and was only 25%. Concentrations of 5 x 10-5 and 10-4 M CuBr2 induced changes in gametophyte development, possibly by re-orientation of growth. Gametophytes treated with 10-5 and 5x 10-5 M CuBr2 took up and accumulated a large amount of copper and ultrastructural observations showed that cytoplasmic damage was limited to twisted swollen thylakoids. The ultrastructure of gametophytes treated with 10-4 M CuBr2 showed absence of a vacuolar compartment. The present observations suggest that P. cambricum gametophytes could be a suitable material for studying physiological and molecular alterations induced by excess copper.