Background Penicillium mameffei (P.mameffei) is an emerging pathogenic fungus that can cause invasive mycosis in patients with AIDS.The epidemiological features of P.mameffei infection in AIDS patients in Guangdong province remain unclear so far.This study aimed to investigate the genetic diversity within a population of 163 P.mameffei isolates obtained from AIDS patients and search for the dominant clinical strains in Guangdong province.Methods One hundred and sixty-three P.marneffeiisolates obtained from AIDS patients in Guangdong province during January 2004 and December 2009 were studied by randomly amplified polymorphic DNA (RAPD) using two random primers (H2 and H22).The degree of similarity between samples was calculated through similarity coefficients from RAPD fragment data and the dendrogram was assessed using the unweighted pair group method with arithmetic mean (UPGMA).Results Two primers showed a high degree of discrimination and good stability.Primer H2 yielded eight different patterns (H2-1 to H2-8) among 163 isolates with the discriminatory power being 0.413.Primer H22 identified seven types (H22-1 to H22-7) among 163 isolates with the discriminatory power being 0.467.Genetic similarity coefficients based on RAPD data among 163 P.marneffei isolates ranged from 0.681 to 0.957,61.96％ of which were no less than 0.83.The discriminatory power of the two primers was 0.524.One hundred and sixty-three P.marneffei isolates were clustered into nine distinct groups (groups I to IX) at the similarity coefficient value of 0.83 and group Ⅰ was the most common,including 101 strains (61.96％).Conclusion The RAPD analyses could provide important information as to the degree of genetic diversity and the relationship among clinical P.mameffei isolates,revealing genetic polymorphism and dominant strains.