The Critically Endangered California condor Gymnogyps californianus has been a focus of intensive conservation efforts for several decades. Genetic studies have played an integral part in these efforts, beginning in 1981 with cytogenetic sexing of all birds. A protocol was optimized for culturing condor lymphocytes and 84 individuals were subsequently sexed through chromosomal analysis. More recently the molecular genetic techniques of DNA-probe hybridization and polymerase chain reaction (PCR) amplification of sex-specific DNA fragments have been used for sex determination, using blood samples taken opportunistically and eggshell membrane material collected non-invasively. In addition, the data obtained by DNA fingerprinting and restriction fragment length polymorphism analysis of mitochondrial DNA have provided insights into the relatedness of the founder birds and the amount of genetic diversity in the entire extant California condor population. Three genetically distinct groups were identified within the founder population using a statistical model to analyse data from multi-locus DNA fingerprints. A mitochondrial DNA probe identified four distinct maternal lineages in the condor population but only two of these lineages remain in the extant ♀♀. As a result of the collaborative efforts of the recovery programme, by mid-1999 the California condor population comprised 162 birds including 50 condors living in the wild.