This study was planned to investigate the extent of cellular damage of the contralateral ovary in unilateral ovarian torsion and to determine possible changes histopathologically by light and ultrastructurally by electron microscopy. Unilateral ovarian torsion was performed in 21 prepubertal, female New Zealand rabbits. One, 8 and 24 hours after the torsion, contralateral ovaries were biopsied. The control group consisted of rabbits without any torsion. Contralateral cellular damage was demonstrated after unilateral torsion. Oocytic nuclei, mitochondria, lysosomes and ovarian stromal cells were also affected when evaluated ultrastructurally.