We studied the edge states and transverse electron focusing in the presence of spin-orbit interaction in a two-dimensional electron gas. Assuming strong spin-orbit coupling we derived semiclassical quantization conditions to describe the dispersion of the edge states. Using the dispersion relation we then make predictions about certain properties of the focusing spectrum. Comparison of our analytical results with quantum-mechanical transport calculations reveals that certain features of the focusing spectrum can be quite well understood in terms of the interference of the edge states while the explanation of other features seems to require a different approach.