The present invention relates to use of particular substituted heterocycle fused gamma-carbolines as described herein, in free, pharmaceutically acceptable salt or prodrug form, and pharmaceutical composition comprising the same optionally in combination with one or more agents, for the prophylaxis or treatment of one or more disorders associated with dementia, particularly behavioral or mood disturbances (e.g., agitation/aggression), psychosis, depression and sleep disturbances among others in patients suffering from dementia.