title: Corrections and clarifications.
abstract: In the article "In vitro transcriptional activation by a metabolic intermediate: Activation by Leu3 depends on a-isopropylmalate" by Ji-Ying Sze et al. (13 Nov. 1992, p. 1143), the second sentence of the legend to figure 1 should have read, "In vitro transcription was carried out as described (6) with 1.2 microg of pUC18 and 0.3 microg of each template per 30-micro1 reaction."