The results of a dynamic mechanical analysis technique (DMA), already developed for estimating the extent of residual cure of phenol-formaldehyde resol resins, depend on the moisture content of the resin. For two resins, different but regular relationships were found between DMA-sample moisture content and the resultant tan delta area, which is measured to determine residual cure of samples. Moisture content also appears to be important for cure determinations by differential scanning calorimetry. The research reported here showed that alkali content, extent of precure, and relative humidity affect the equilibrium moisture content of phenol-formaldehyde resol resins.