Abstract Context: Many girls with Turner syndrome have follicles in their ovaries at adolescence. Objective: Our objective was to study which girls might benefit from ovarian tissue freezing for fertility preservation. Design: Clinical and laboratory parameters and ovarian follicle counts were analyzed among girls referred by 25 pediatric endocrinologists. Subjects and Setting: Fifty-seven girls with Turner syndrome, aged 8–19.8 yr, were studied at a university hospital. Interventions: Ovarian tissue was biopsied laparoscopically, studied for the presence of follicles, and cryopreserved. Blood samples were drawn for hormone measurements. Main Outcome Measures: Presence of follicles in the biopsied tissue related to age, signs of spontaneous puberty, karyotype, and serum concentrations of gonadotropins and anti-Müllerian hormone were assessed. Results: Ovarian biopsy was feasible in 47 of the 57 girls. In 15 of the 57 girls (26%), there were follicles in the tissue piece analyzed histologically. Six of seven girls (86%) with mosaicism, six of 22 (27%) with structural chromosomal abnormalities, and three of 28 with karyotype 45X (10.7%) had follicles. Eight of the 13 girls (62%) with spontaneous menarche had follicles, and 11 of the 19 girls (58%) who had signs of spontaneous puberty had follicles. The age group 12–16 yr had the highest proportion of girls with follicles. Normal FSH and anti-Müllerian hormone concentrations for age and pubertal stage were more frequent in girls with follicles. Conclusions: Signs of spontaneous puberty, mosaicism, and normal hormone concentrations were positive and statistically significant but not exclusive prognostic factors as regards finding follicles.