The 400 kW Pico OWC plant was built in 1995-1998 with support from the European Commission and co-funding from EDP (Electricidade de Portugal) and EDA (Electricidade dos Açores), respectively the national and regional utilities. Instituto Superior Técnico (IST), Lisbon was responsible for the conception and basic engineering studies of this plant and co-ordinated the project. The plant is a bottom-mounted shoreline structure, equipped with a Wells turbine with guide vanes. In 2004-2006 a set of relevant repair works under the co-ordination of the Wave Energy Centre, in the scope of a national funding scheme, lead to the successful recovery and commissioning of the plant included a monitoring program indicating reasonable performance. Relevant data has been recorded, such as instantaneous values of the water free surface elevation inside the pneumatic chamber, the air pressure in the chamber, the air pressure (static and dynamic) in the turbine duct, the rotational speed of the turbine and the electrical power output delivered to the grid. Due to necessary modifications of the support structure of the turbo-generation unit, the tests have been discontinued in late 2006. Excessive vibrations at higher turbine speeds inherited from the original mechanical project presently the focus of ongoing efforts until end of August 2007.