The receptive component of the Cy transposable element system (rcy:Mu7) at the Bz locus of Zea mays L. is 2.2 kb and has long terminal inverted repeats. The insertion is flanked by a 9 bp duplication. In the presence of an autonomous Cy element in the genome, rcy:Mu7 is excised from bz-rcy in a manner consistent with a model suggested previously. The termini of rcy:Mu7 have 85% sequence similarity with the Mu1 element of Z. mays. This is consistent with the observation that Mu1 can behave genetically like a receptive component of the Cy system.