We have started genetic mapping of the citrus genome by segregation analysis of different molecular markers (RAPDS, RFLP and isozymes) in the progeny of FAO 30573 hybrid (Citrus reshni x Pancirus trifoliata) and pummelo (C. grandis) used respectively as paternal and maternal parents. A total DNA library and a cDNA library were constructed from sweet orange (C. sinensis) leaves of the Valencia Late clone. The screening of probes w.as made on the parent genotypes using 4 restriction enzymes. Among 85 tested probes, 85 % of cDNA probes and 10 % of genomic probes revealed polymorphic patterns. Segregation analysis w.as performed w.ith the MapMaker program. The map of the intergeneric hybrid comprised 95 foci linked in 12 groups : 7 isozymes, 45 cDNA/RFLPs, 1 rDNA/RFLPs, 40 RAPDs and 2 inter-microsatellite sequences. The map of pummelo comprised 34 markers making 7 linkage groups : 3 isozymes, 13 cDNA/RFLP, 15 RAPDs and 3 inter-microsatellite sequences. Only the first map shows evidence of skewed segregation within some linkage groups (37.5% of total markers). Some applications of citrus genetic maps are given.