Turner syndrome is a common chromosomal disorder in females. The main phenotypic characteristics are short stature, lack of sexual development during puberty, facial dysmorphism and malformations of the skeletal system, heart and kidneys. Karyotype variants of Turner girls are well known and consist of monosomy X in complete or mosaic form as well as different structural changes of the X chromosome. Chromosomal changes might have significant influence on the growth and pubertal development of Turner girls. The incidence of spontaneous puberty inTurner girls is estimated to be between 5 and 20%. We have analyzed 48 girls with Turner syndrome. Karyotype from the peripheral blood lymphocytes and G banding were performed according to the standard procedures.In cases where Y chromosome was present, FISH method using Y probe was used. Ten girls developed puberty at age 10-14 years. The karyotype of these girls was 45,X0 in 2(20%), 45,X/46,XX in 2(20%), 45,X/46,XiXq in 4(40%), 45,X0/47,XXX in 1(10%), and 46,XXr in 1(10%). No preponderance of specific karyotype was seen, however it seems that isochromosome Xq appears more frequently in Turner girls with spontaneous puberty. More cases are needed in order to confirm this observation. There are some observations that karyotype in the ovary should carry normal XX line for the development of puberty. In Turner girls with spontaneous puberty menstruation is irregular, cycles are often anovulatory and cease within few months or years increasing risk for endometrial malignancy. New methods like biopsy through laparoscopy might be useful in elucidating spontaneous puberty in Turner girls in order to design appropriate treatment.