Basic solutions are obtained for edge-cracks lying along the primary slip p
lane in a single crystal. The study is motivated by Stage I fatigue crack g
rowth wherein crack orientation is controlled by the slip direction and con
tinued growth is dependent on the crack overcoming barriers to slip. Plasti
city is assumed to occur as slip along planes inclined at 45 degrees to the
surface. Problems where slip is limited to persistent slip bands are consi
dered side-by-side with the problem where slip is not confined. Results for
both monotonic and cyclic loadings are presented, with emphasis on the cra
ck tip opening and sliding displacements. Both small and large scale yieldi
ng are considered. Preliminary results are given for interaction with barri
ers to slip, such as a grain boundary.