Adventitious lung sounds indicative of lung congestion are detected using an implantable sensor. The sensor is adapted to be positioned adjacent to a pulmonary system and to output signals indicative of lung sounds in response to pulmonary system activity. A controller receives the signals and processes the signals to detect the presence of adventitious lung sounds. A respiratory cycle sensor operating in conjunction with the lung-sound sensor enables classification of an adventitious lung sound according to its time occurrence within the respiratory cycle. Posture sensing in conjunction with lung-sound sensing provides valuable additional information as to the severity of the lung congestion.