We treated the invasive wetland grass, Phragmites australis (Common Reed), with herbicide in 99 (total of 14 ha) interdunal wetland swales of Sandy Neck barrier beach on Cape Cod, MA from 2002–2008. The herbicide applications have significantly reduced the number of Phragmites stems within invaded swales, with parallel reductions in personnel and chemical costs of the control program. After seven years of treatment, we have achieved substantial containment and suppression of Phragmites, but the plant persists in all but a few of the treated swales. Whether eradication or near-eradication can be ultimately achieved remains uncertain.