Economic and ecological preconditions are considered for the transition from monoproduct oil shale mining to polyproduct Estonian oil shale deposits. Underground water, limestone, and underground heat found in oil shale mines with small reserves can be operated for a long time using chambers left after oil shale extraction. The adjacent fields of the closed mines can be connected to the operations of the mines that are still working. Complex usage of natural resources of Estonian oil shale deposits is made possible owing to the unique features of its geology and technology. Oil shale seam development ir carried out at shallow depths (40-70 m) in stable limestones and does not require expensive maintenance. Such natural resources as underground water carbonate rocks, heat of rock mass, and underground chambers are opened by mining and are ready for utilization. Room-and-pillar mining does not disturb the surface, and worked oil shale and greenery waste heaps do not breach its ecology. Technical decisions and economic evaluation are presented for the complex utilization of natural resources in the boundaries of mine take of the ＇＇Tammiku＇＇ underground mine and the adjacent closed mine N2. Ten countries have already experienced industrial utilization of oil shale in small volumes for many years. Usually oil shale deposits are not notable for complex geology of the strata and are not deeply bedded. Thus complex utilization of quite extensive natural resources of Estonian oil shale deposits is of both scientific and practical interest.