THIN WALLED MOLDS HAVING A THICKNESS WITHIN A RANGE FROM ABOUT 0.4 MM. TO ABOUT 4 MM. AND HAVING A HEAT CAPACITY LESS THAN THE HEAT CAPACITY OF THE MOLDED ARTICLE ARE PROVIDED IN APPARATUS FOR INJECTION MOLDING OF PLASTIC FOAM. IN CERTAIN EMBODIMENTS, HEAT TRANSFER FLUID IS CIRCULATED IN A ZONE ADJACENT THE THIN WALLED MOLD FACE. IN SOME EMBODIMENTS OF THE INVENTION, AN OUTER SHELL CAN PROVIDE SUPPLEMENT STRUCTURAL STRENGTH, WHILE BEING INSULATED BY CLOSED PORE INSULATION FROM THE TEMPERATURE CHANGES AND HEAT CAPACITY FEATURES OF THE MOLD FACE.