A series of field suction pile installation tests have been conducted inside the Onsan harbor located in southeastern Korea during the summer of 2001. The suction piles were made of steel, having inside diameters ranging from 0.5 meters to 2.5 meters and the length of five meters. The seafloor soil condition at the site is predominantly silty sand. Instrumentation includes the detailed measurement of the applied pressure vs. pile penetration and retrieval length relationships; the pile alignment during installation through a tiltmeter; and the pore water pressures both inside and outside the pile.