Forty-one procedures were performed to revise malfunctioning filtering blebs in 37 eyes. Thirty-two procedures were undertaken on underfiltering blebs, seven on overfiltering blebs, and two on normally functioning but otherwise unsatisfactory blebs. Revision procedures were successful in 24 of 32 underfiltering blebs, four of seven overfiltering blebs, and one of two normally functioning but unsatisfactory blebs.