The expression of alpha 1,3 fucosylated type 2 antigens is generally thought to be restricted to myeloid cells among normal human haemopoietic tissue. The distribution of three fucosylated antigens [Lewis X (Le(x)), sialyl Lewis X (sLex) and VIM2] was investigated among nine human leukaemia cell lines by fluorescence activated cell sorting (FACS) analysis. As expected, all myeloid cell lines were positively stained by antibodies against these three fucosylated antigens. Unexpectedly, two T-lymphocytic cell lines (CCRF-CEM and MOLT4) were found to express Le(x) and VIM2, and the plasma, B-cell line, RPMI 8226, expressed all three fucosylated antigens. Enzymatic and RNA analyses [Northern blot and reverse transcription polymerase chain reaction (RT-PCR)] were used to evaluate possible control points in the biosynthetic pathway for Le(x) and sLex. beta 1,4 Galactosyltransferase (beta 1,4GalT, an enzyme involved in the synthesis of the core oligosaccharide of the three fucosylated antigens) activity and the corresponding mRNA were found in all of the leukaemia cell lines, regardless of whether or not they expressed the fucosylated antigens. In contrast, alpha 1,3 fucosyltransferase (GDP-fucose:beta-D-N-acetylglucosaminide 3-alpha-L-fucosyltransferase; alpha 1,3FT) activity and the corresponding mRNA were found only in those cell lines expressing fucosylated antigens. Based on RNA analysis, acceptor specificity and N-ethylmaleimide inhibition studies, it was concluded that all of the cell lines expressing fucosylated antigens contained alpha 1,3FTIV (myeloid alpha 1,3FT). This appeared to be the major alpha 1,3FT in the myeloid and T-lymphocytic cell lines. Interestingly, even though both types of cell lines expressed the same alpha 1,3FT, only the myeloid cell lines expressed sLex, whereas all of the myeloid and T-lymphocytic cell lines expressed a structural analogue of sLex (i.e. VIM2). In contrast to the myeloid and T-cell lines, RPMI 8226 cells contained more than one fucosyltransferase activity. Acceptor specificity analysis demonstrated that this cell line contains alpha 1,3 and alpha 1,4FTs. Among the fucosyltransferases expressed by RPMI 8226, alpha 1,3FTIV accounted for only a small amount of the total activity. The results of this study demonstrate that fucosylated antigens, which are generally considered to be myeloid specific antigens, are also expressed by lymphocytic leukaemia cell lines, and that the types of fucosylated antigens and fucosyltransferases expressed in these cell lines vary.