Program evaluation, a technique used to measure the effectiveness of governmental programs, is applied to estuarine management. Point source loadings of oxygen demanding organic material and ambient conditions of bottom water dissolved oxygen in the upper reaches of the Narragansett estuary were examined over recent decades to determine the effects of a sweage treatment plant in reducing pollution. Two tests of program outcome are presented. The first demonstrates that a statistically significant increase in bottom water dissolved oxygen is correlated with a sewage treatment plant upgrade. Other possible causes for this change are examined and eliminated. Apparently, enhanced sewage treatment is the cause of an improvement in dissolved oxygen, one measure of ambient water quality. The second analysis shows that these improvements in water quality exceed those that could be attributed to improved background conditions caused by reduced loading from the major river. Estuarine segments lacking improved bottom water dissolved oxygen receive combined sewer overflows and possibly loads from small tributaries. Present conditions of bottom water dissolved oxygen, although improved throughout much of the upper estuary, are not sufficient to meet desirable standards.