Two phenomena of diffraction contrast arising a t or near 111-V compound heterostructure boundaries are described and quantitatively analyzed. In the first observation alS-fringe contrast at boundaries inclined to the electron beam is discussed. Theoretical fringe profiles are generated according to the theory by Gevers et al. in 1964, which are then compared with experimental profiles. Applications to the characterization of AlGaAslGaAs and InGaAsPlInP interfaces regarding composition, abruptness, and lattice tilt are presented. In the second study a new and very sensitive characterization technique for the direct determination of the strain in strainedlayer structures is described. The method uses electron microscope images of 90"-wedges, which exhibit a shift in the thickness contours due to strain relaxation a t the edge, and compares these to images which are obtained theoretically by implementing finite element strain calculations in wedges in the dynamical theory of diffraction contrast. The considerable potential of this method is demonstrated on the strain analysis of strained GaInAdGaAs structures. alS-Boundary, Strain analysis, Finite element method, 90O-wedges