As part of an EU project (QLK1-2001-01643), the effect of storage time and temperature on the microwave dielectric properties of thawed frozen cod ( Gadus morhua) were studied. The measurements were made in the time domain, collecting the reflected pulse from the sample surface when an incident step pulse was applied through an open-ended coaxial sensor. The data were transformed using the statistical method of principal component analysis. The principal components were regressed (principal component regression) against time and temperature of storage and various sensorial variables to obtain calibration equations. These calibrations were validated using the method of internal cross-validation.