The report gives results of a follow-up of the 1986 demonstration of radon reduction techniques in 10 houses in Clinton, New Jersey. Initial radon levels in the 10 houses ranged from 400 to 2200 pCi/1. Radon reductions of more than 95% were achieved by using a variety of subslab ventilation techniques. Since January 1987, the radon levels in the 10 houses have been monitored with alpha track detectors. The detectors have been installed and removed quarterly. Three detectors were used on the lowest level of each house, and three on the next higher level. Results of the comparison between the radon concentration measured during the first and second quarters of 1987 showed that most of the houses had slightly higher concentrations during the second quarter. These results are contrary to expected trends. Two houses with slightly elevated radon levels received additional radon reduction applications at the end of the second quarter of 1987: in one house, the radon concentration was successfully reduced, and in the other, the concentration was essentially unchanged.