The immunochromatographic (ICT) filariasis test is a rapid screening tool that will be useful for defining the prevalence and distribution of Wuchereria bancrofti as part of the global program to eliminate lymphatic filariasis. To address questions about its usefulness for monitoring control programs, we used the ICT filariasis test to assess residual antigen levels following antifilarial treatment. Our results demonstrate that antigen levels persist in microfilaria-negative persons for up to three years after treatment. Different strategies for monitoring control programs may have to be considered.