We present theoretical studies on waveguides and waveguide bends in two-dimensional photonic crystal slabs. The waveguides are created by either filling up or decreasing the sizes of air holes. Our designs focus on using the frequency range where the waveguide mode is nonleaky. It is shown that high transmission through the sharp bend can be obtained for some frequency ranges in the triangular lattice slabs. The waveguides in square lattice slabs are also investigated.