A novel dual-amplitude pulse interval modulation (DAPIM) for optical wireless communications is discussed. The symbol structure, the spectral properties, the bandwidth requirement and error performance of DAPIM in a nondispersive channel are presented. DAPIM shows a better compromise between bandwidth and power requirements compared with OOK, PPM, and PIM. DAPIM with 5 bits and 6 bits persymbol is attractive in terms of optical power and bandwidth requirements.