This paper presents a description of the Airborne Bathymetric System (ABS) laser sounder system hardware. The system was designed for installation and operation aboard a P-3 aircraft. In normal operation, the aircraft flies at a 500 meter altitude and a speed of 180kts (100m/s). With these operation parameters and a 270m survey swath width, the system surveys at about 100km2 per hour. For an average daily flight of four hours, 400km2 of coastal ocean can be mapped. The laser sounder system collects 400 Light Detection And Ranging (LIDAR) measurements a second for up to 4 continuous hours. It has a horizontal resolution of approximately 10m and a vertical resolution of about 0.54m, at a 15° scan angle. The LIDAR system sports a KD>3 (K=diffuse attenuation coefficient, D=depth penetration) performance. The ABS laser sounder has taken advantage of new parallel processing computer architectures, improved waveform digitizers, and optical disks. In this system, digital real time processing has replaced past analog processing. This is due to the realization that it is easier to build and implement an adaptive digital algorithm than it is to build an adaptive hardware analog processor. The system hardware consists of a transceiver, Sensitivity Time Control (STC) circuit for the gateable Photo-Multiplier Tube (PMT), dual computer system (data collection system and real time read after write processing system) using six single board computers, 400 mega-sample per second waveform digitizer, High Density Digital Recorder (HDDR), Global Positioning System (GPS) receiver/pre-processor, aircraft Inertial Navigation System (INS) interface/pre-processor, millisecond resolution clock, two information displays and an optical disk.