Abstract: Potato spindle tuber viroid (PSTVd) was detected in potato plants grown in Egypt using return -polyacrylamide gel electrophorsis (R-PAGE) and molecular techniques. The method involved the extraction of circular nucleic acids followed by electrophoretic analysis of the extracts on 5 % polyacrylamide gel. A reverse transcription-Polymerase chain reaction (RT-PCR) assay was used for the isolation and identification of PSTVd cDNA from infected plant materials using specific primer to PSTVd. A major cDNA product of approximately 360 bp. These products were Successfully hybridized with digoxigenin labeled PSTVd cDNA probe.