The white block skipping (WBS) method of coding binary facsimile images consists of breaking each scan line intoNpicture-element (pel) blocks, then using "0" as the code word for all-white blocks and "1" followed by the binary pattern in the block for non-all-white blocks. In the first part of this paper, we derive (based on a first-order Markov source model) the optimum block sizeNand its corresponding minimum bit rate as functions of the average white and black run lengths of the image. In the second part of this paper, we propose a modified coding scheme where all-white scan lines are essentially skipped. This modified scheme is found to be as efficient as run length coding for transmitting texts.