In addition to reporting, in accompanying papers, their individual analyses of 
mapping the neurofibromatosis type 1 (NF1) gene on chromosome 17, members of the 
International Consortium for NF1 Linkage contributed their data for our joint 
analysis to determine the exact sequence of flanking markers and to obtain 
precise estimates and confidence limits of the recombination fractions for the 
closest markers, in anticipation of clinical use. With specimens from 142 
families and more than 700 affected persons, eight teams used 31 markers in the 
pericentric region of chromosome 17 to perform 13,838 genotypings. With the 
combined data, we used the computer program CRI-MAP to build the most likely 
sequence of loci by sequentially adding single loci to a fixed pair of loci and 
separately calculating the likelihood of all permutations of four consecutive 
loci. The best order is pter-pA10-41-EW301-centromere 
(p17H8)-pHHH202-NF1-EW206-EW207-EW203++ +-CRI-L581-CRI-L946-HOX2-NGFR-qter. The 
total genetic distance from pA10-41 to NGFR is 26 cM in males and 56 cM in 
females, and the overall difference in sex-specific maps is statistically 
significant (P = .006). The upper 99% confidence limits of the recombination 
fraction of the closest proximal marker, pHHH202, is 4%, and that for the 
closest distal marker, EW206, is 9%. These limits should decrease with the use 
of additional probes and the further evaluation of DNA from the six persons 
showing multiple recombinations within short genetic distances. Clinical 
application is technically feasible with currently available markers, although 
its appropriate use for prenatal and presymptomatic diagnosis requires further 
discussion and evaluation.