Analysis for relative intensity noise (RIN) is an important consideration for the optimum design of system performance in most of the optical communication systems. Monolithic integration of optical and electronic devices leads to new characteristics such as internal electrical and optical feedback among the components. This will also affect the noise performance of the device. A quantitative analysis for the RIN performance of an optoelectronic integrated device composed of a laser diode (LD) and a heterojunction phototransistor (HPT) is presented. We consider effects of the internal optical feedback from the LD to the HPT, and of avalanche multiplication in the device. It is found that the internal optical feedback improves the RIN of the device, especially near the threshold. © 1997 Elsevier Science Ltd.