Cloning and sequence analysis of cDNA showed that the brain type of ryanodine receptor (RYR) is expressed in human Jurkat T-lymphocyte cells. Fura-2 measurements revealed that the RYR in T-cells functions as a ryanodine-sensitive, caffeine-insensitive Ca2+ release channel. Furthermore, ryanodine stimulated proliferation and altered the growth pattern of cultured human T-cells when added together with FK506.