A comparison of radiocarbon dates obtained from Egyptian archaeological samples and from contemporary tree growth-rings shows significant discrepancies over an extended period of time. On geophysical grounds, however, a single calibration curve for the whole of the Northern Hemisphere of the Earth is predicted. Further, there is no justification for suspecting tree growth-rings used for calibration to be contaminated in any way. The author concludes that the discrepancies are due to chronological errors in assigning ages to the Egyptian samples and the dendrochronological samples, and shows that that calibration before about 500 B.C., may be justifiably questioned. Additional C-14 calibration anomalies resulting from measurements of a number of dendrochronological samples are also discussed to indicate, that if they are correct, the fundamental principles of the dating method require revision.