Method and apparatus is provided for reinforcing a structural member of a vehicle body by the use of adhesively bonded together glass macrospheres of 3 to 9 mm. in diameter. The adhesive is not more than about 40% by weight of the mixture so that voids remain between the adjacent macrospheres to permit airflow through the reinforcement and the reinforced structural member upon curing adhesive. The adhesive may be curable at ambient temperature or may be a high temperature curable adhesive which is cured in a vehicle body paint curing oven to bond the macrospheres to one another and to the structural member. The adhesion of the macrospheres to the structural member may be facilitated by an epoxy coated flexible sheet material lining the walls of the structural member. The adhesive coated macrospheres may be closely packed into the structural member by pouring or blowing.