A novel reversible binary image data hiding scheme using run-length (RL) histogram modification is presented in this paper. The binary image is scanned from left to right and from top to bottom to form a sequence of alternative black RL and white RL. Combining one black RL and its immediate next white RL, we form one RL couple, thus generating a sequence of RL couples. The length of each couple is fixed during data embedding in order not to fail the reversibility. Two procedures are adopted to achieve reversibility: 1) only involve those RL couples in data embedding in which the length of couple is not shorter than threshold T1; 2) increase white RL of isolated white pixels from one to two. Another parameter T indicates where to embed data in black RL histogram. Adjusting T1 and T may result in optimum performance of pure embedding rate versus visual quality of marked image. The proposed scheme works for text, graphics, and their mixture, both halftone and non-halftone binary images. Experimental works have shown its superior performs over the prior-arts.