HIV epidemic related to nosocomial transmission in Romanian nursed children represents up to now more than 50% of paediatric AIDS cases in Europe. Although the sources of this epidemic are obscure, HIV-1 subtype F, a minor form in Brasil and Africa, realised a founder effect in this risk group, thus becoming the major form in Romanian epidemic. This study presents the results of the virus isolation from HIV-infected children in Northeast Romania. Heteroduplex mobility assay (HMA) was performed in order to establish HIV-1 viral subtype for 6 isolates. All tested HIV-1 strains were proved to belong to F subtype. So, our study confirm that HIV-1 subtype F is responsible for the epidemic in the risk group of Romanian nosocomially infected children.