In the report "Transfection of v-ras(H) DNA into MCF-7 human breast cancer cells bypasses dependence on estrogen for tumorigenicity" by A. Kasid et al. (10 May, p. 725), a line connecting two sentences was inadvertently omitted from the text. On p. 726, column 1, line 9, the sentence beginning "Densitometric scans of the blots " should have continued as follows: "showed that the transfectants expressed ras(H) RNA at levels 10 to 12 times higher than wild-type MCF-7 cells (Fig. 1E) or MCF-7(gpt) cells. Wild-type MCF-7 cells contained a low level of endogenous c-ras(H) RNA and neither its expression nor that of the exogenously acquired v-ras(H) gene was altered by E(2) treatment (Fig. 1E)."