The technique of sputtering is described. Opaque, optically good films were sputtered in a residual atmosphere of air from cathodes of Sb, Bi, Cd, Au, Pb, Pt, Ag, Sn and Zn in about an hour; from Co, Cu, Ir, Fe, Ni, Se and Te in two hours or so; and from Mo, Ta and W in several hours. Al, Be, C, Cr, Mg and Si sputter very slowly in air. In a residual atmosphere of Hg or He or A, opaque films of Al, Cr and Si were sputtered in a few hours. Evidence is presented which indicates that a majority of the sputtered particles are of molecular or atomic dimensions. The transmission of films of Pt, Ta and Cr was nearly constant for wave‐lengths from 0.5 to 2.2μ; films of Si and C were relatively transparent from 1.0 to 2.2μ.