Abstract: The interlocking environmental container allows milk, juice and various food containers to be saved for use as building blocks for such items as children's toys, lawn furniture or sheds. Tongue and groove construction of one pair of opposing sides combined with top and bottom mounting means and special corner pieces allows the containers to be built into semi-rigid structures. The invention is both a retail marketing aid and a conservation aid. Plastic containers are preferred for the strongest building blocks, but any other container material can be used.