The Guntong field, the largest waterflood field in offshore peninsular Malaysia, with an oil-in-place (OIP) of about 200 million m(3), has been producing since 1985. The field contains 13 stacked reservoirs with small gas caps and limited aquifer support. This paper describes some of the significant reservoir, geologic, and facility challenges faced during development and management of this complex reservoir system. A combination of five-spot and peripheral waterflood patterns was selected to provide the required areal coverage, and reservoirs were commingled into two operational groups. Key reservoir management strategies to maximize performance include determination of optimum target reservoir pressures, use of a PC-based program to guide production and injection targets, and meeting pattern-balancing and capacity-enhancement programs. The response to the reservoir management efforts has been favorable, with an all-time-high production rate of 14 000 m(3)/d recorded in 1994.