In the present paper we report an extremely rare case of mosaicism of 45,X/47,XX,+13 in a 28-year-old women. The patient was referred for cytogenetic evaluation for secondary amenorrhoea. The patient was found to have some mild characteristic features of Turner syndrome such as wide carrying angle and short stature. Ultrasound examination revealed the presence of a small sized uterus and bilateral streak ovaries. G-banded chromosome analysis revealed a mosaic female karyotype involving two different cell lines. One cell line (72% of analysed metaphases) presented monosomy of X while the remaining 28% of cells showed trisomy of chromosome 13. Fluorescence in situ hybridization (FISH) with locus specific probe for trisomy 13 and CEP X for monosomy X substantiated the results obtained from karyotyping.