This case history includes the design, testing, job execution, and post-job results of a successful foamed spacer/cement application. During this application, a liner was cemented across a productive formation in which a significant amount of low density mud was lost during the drilling phase. During a deep well drilling campaign in Argentina, a naturally fractured formation located between 3828 m and 4290 m experienced severe lost circulation. Once this section was drilled, a single stage cement slurry needed to be placed without major cement slurry losses to the formation. The section then needed to be successfully sealed from the shoe to the top of the liner. Additional consideration was given to minimizing fluid-loss damage to a potentially productive zone that consisted of low-pressure microfractures and large fractures. One of the most difficult challenges in a cementing operation is getting successful cementing results across lowpressure formations that have lost circulation tendencies. Although alternative methods involving stage tools and top squeezes can be considered, liner applications tend to complicate the operational phase because of liner hangers, tool outside diameter (OD) geometries, plugs, and pressure activation requirements. An additional challenge was to effectively remove the residual mud filter cake from the annulus of a 15° uncentralized casing in a deviated wellbore. After all potential challenges to this liner application were addressed, a foamed cement/spacer system was determined to be the best solution for meeting all objectives and completing the liner application. This lightweight cementing system possesses many benefits, including (1) superior mud displacement, Copyright 2001, Society of Petroleum Engineers, Inc. This paper was prepared for presentation at the 2001 Latin American and Caribbean Petroleum Engineering Conference held in Buenos Aires, 25 March. This paper was selected for presentation by an SPE Program Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Papers presented at SPE meetings are subject to publication review by Editorial Committees of the Society of Petroleum Engineers. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment.