Potato spindle tuber viroid (PSTVd) was detected in potato plants grown in Egypt using return-polyacrylamide gel electrophoresis (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 a specific primer to PSTVd. A major cDNA product of approximately 360 bp was successfully hybridized with digoxigenin labeled PSTVd cDNA probe.