The South Marsh Island 205-A platform is located in the Gulf of Mexico off the coast of Louisiana in a water depth of 437 ft. Instead of launching the jacket from the transportation barge, the jacket was lifted from the barge with two derrick barges. The jacket consists of four main legs which frame directly into four skirt sleeves. This is the first such jacket to be designed for the Gulf of Mexico. It is the largest jacket by weight and water depth to be lifted in the Gulf of Mexico and is the deepest four pile jacket installed in the Gulf of Mexico to date. The design and configuration of the jacket, the development and analysis of the skirt sleeve to leg connection and the installation of the platform are presented in this paper. INTRODUCTION South Marsh Island block 205 is operated by Mobil Exploration & Producing U. S., Inc. The contract for the design of the South Marsh Island 205-A platform was awarded to McDermott, Inc. in March, 1988. In an effort to reduce fabrication and installation costs and to enhance the financial return of the field, the feasibility of a lifted jacket with four skirt piles and no main piles was investigated. Gulf of Mexico fabrication and installation contractors were contacted for input concerning fabrication capabilities, limitations, marine equipment capacity and availability. At the same time, Mobil Research and Development Corporation (MRDC) was contacted for information on a skirt sleeve to leg connection that had been developed for the North Sea. Through preliminary analysis along with contractor and MRDC input, it was concluded that the concept was feasible and that cost savings could be realized. In another effort to reduce costs, an existing deck was salvaged and refurbished for reuse. The deck was a two level, eight leg drilling/production deck that was originally designed for simultaneous operations. For the removal of the deck, it was cut off 2 ft. below the cellar deck and placed on 2 in. circular plates to be later installed on top of the South Marsh Island 205-A jacket. Elevation views of the platform are shown in Figure 1. The eight leg deck is supported by the four corner legs of the jacket and four false legs which are braced into the corner legs below the waterline. The legs are tapered from 36 in. diameter at the top to match the deck legs to 80 in. diameter at the bottom. The spacing of the legs at the top of the jacket is 45 ft. × 125 ft. The legs are battered 1:6 in the transverse direction and 1:12 in the longitudinal direction which results in an essentially square base that is 210 ft. × 208 ft. The jacket weighs 3810 s. tons in air as weighed with electronic load cells prior to loadout. In order to lower the weight of the jacket for lifting purposes as well as on-bottom weight, approximately 45% of the jacket steel is 50 ksi material.