DNA Microarray images are used to identify and monitor gene activity, or expression. In a single experiment, a large number of microarray images may be produced. Storage and archiving of these images are an important problem for researchers. Since microarray images can have a wide variety of nearly random patterns with no discernible structures, general entropy coders, e.g. Bzip2, or generic image compressors, e.g. JPEG-LS, do not perform well. In this work, we investigate performance of the inversion coding technique in lossless com pression of DNA microarray images. We show that inversion coding outperforms commonly used entropy coders and image compressors.