The experience with cytogenetic and flow cytometry methods used for th
e diagnosis of Fanconi anemia (FA) in one center is summarized. The te
sts consist of chromosomal breakage and cell cycle studied after sensi
tization by the introduction of nitrogen mustard into phytohemagglutin
in-stimulated blood-cell cultures. The cytogenetic test was shown to b
e reliable in ascertaining the diagnosis of FA. Flow cytometry studies
showed a marked increase in the percentage of cells in G2/M phase in
FA patients after sensitization by nitrogen mustard. This increase, ho
wever, could not be detected in three FA patients with myelodysplasia
or acute leukemia and the results were ambiguous on three occasions.