This essay seeks to assess that which did not change and that which changed radically in the thinking of Clark and associates between 1978 and 1995 in regard to "tumor progression in the melanocytic system" and its corollaries, namely, melanocytic dysplasia, dysplastic nevus, and dysplastic nevus syndrome as epitomized in two of the most recent publications by them in Seminars in Diagnostic Pathology (1993) and the British Medical Bulletin (1995).