-We present a constraint adaptive image segmentation technique designed to achieve the combined purposes of color image coding/compression, indexing and content-based retrieval. An image is segmented into homogeneous squared regions of variable sizes such that it can be encoded very emciently [7]. From the segmented image, we derive an effective and efficient image content description feature termed the region and color co-occurrence matrix (RACOM) as image index for content-based indexing and retrieval. Experimental results are presented to demonstrate that RACOM is a very effective image content description features and has comparable performance to state of the art methods, colour correlogram [8] and MPEG7 colour structure histogram [9], in content-based image retrieval from large image databases.