Cells from patients wtih Fanconi's anemia are unusually sensitive to agents 
which are capable of crosslinking DNA. This increased sensitivity can be 
detected both by cytogenetic and flow cytometric methods. An elevated frequency 
of chromosome aberrations, which is further exaggerated by exposure of cells to 
DNA crosslinking agents, is a general feature of Fanconi's anemia. Information 
about the formation of sister chromatid exchanges in this disease is less 
consistent. Cytogenetic analysis of cells from patients with Fanconi's anemia 
can be compromised by a low mitotic index. This is reflected in an accumulation 
of cells In the G2 phase of the cycle, after exposure to the bifunctional 
alkylating agent, mitomycin C. New methods for differentiating individuals with 
Fanconi's anemia from unaffected individuals should be of empirical use and 
might also facilitate mechanistic studies of this disease.