The indium(I) compound, In(C5H4CMe3), has been prepared from the corresponding lithium cyclopentadienyl reagent Li(C5H4CMe3) and InCl in OEt2. Characterization data have included partial elemental analyses (C, H), physical properties, IR, H-1 NMR and mass spectroscopic data, oxidation reactions with dilute aqueous HCl and a single-crystal X-ray structural study. The colorless crystal of In(C5H4CMe3) consists of infinite zigzag chains. There are no interstrand In ... In interactions. The compound crystallizes in the monoclinic space group P2(1)/n with four formula units in the unit cell with dimensions of a 6.139(1), b 9.765(6), c 15.543(3) angstrom, beta 92.87(1) and rho-calcd 1.68 g/cm3.