The problem of a steady propagating semi-infinite crack between two bonded, viscoelastic infinite strips subjected to mode III deformation is investigated. A Wiener-Hopf equation is formulated and solved in closed form by means of a Cauchy-type integral. The integral is evaluated yielding the stress intensity factor for various material combinations including a homogeneous Maxwell material, two bonded Maxwell materials, a bonded elastic and Maxwell material and two standard solids. The correspondence principle is employed to obtain the stress intensity factor value for a standing crack (i.e. v = 0). Results are presented in graphical form for some cases of interest.