A custom CMOS image sensor designed for low power endoluminal applications is presented. The fabricated chip includes a 320×240 pixel array, a complete read-out channel, a 10-bit ADC converter, a series of DACs for internal references and digital blocks for chip control. The complete functionality of the chip is guaranteed through 7 signal pins, used for the I2C-like input and LVDS output interfaces. Prototypes were produced using UMC 0.18 m-CIS (CMOS Image Sensor) technology for both monochrome and colour-RGB versions. Due to its high sensitivity, a pinned photodiode was implemented. The imager was electrically and optically characterized and preliminary ex-vivo tests were performed. Characterization results show state-of-the-art performance in terms of power consumption (<40 mW for the core), which is less than half compared to off-the-shelf sensors, and light sensitivity (0.1 lux@555 nm for the monochrome imager), which makes sensor performance comparable to CCD technology performance for single chip endoluminal applications.