Histochemical method of cytochrome oxidase demonstration was used to study its distribution in frontal sections of tectum of the midbrain in cat in normal conditions and after unilateral enucleation. Basic layers of this formation were demonstrated in normal conditions similar to those revealed using classical histological methods. After unilateral enucleation rostral, middle and caudal parts of superior colliculus were stained differently. Contra- and ipsilateral surface layers in rostral and caudal parts were stained also with different intensity. Alteration of lightly and intensely stained patches appeared in middle part. Peculiarities of staining in cytochemical cytochrome oxidase demonstration in superior colliculus of tectum of the midbrain in enucleated animals are likely to reflect peculiarities of this structure afferentially by retinotectal, geniculotectal and geniculocortical fibres.