In this paper, we study the possibility of using θ-index for retrieval of imagebase. Image retrieval is related to partition in an image space. If there exists a mapping from an image space to a feature space, the partition in the image space can be converted into a partition in the feature space. To retrieve an image, some features of the image must be identified. Feature identification can be considered as optimal assignment of some indices to images. This is equivalent to an optimal partition of image space into mutual exclusive regions, each corresponding to particular values of a set of indices. In our system, the feature extraction is implemented by a two-dimensional θ-transformation. The time complexity for a θ-transformation is very low. Therefore, for a certain class of images, θ- transformation is a very efficient algorithm for image indexing.