A method of manipulator path planning is presented, and a trajectory interpolation algorithm is given. Closed-form and numerical path optimization methods are discussed. This new method consists of the use of trigonometric splines of order 4. Continuity of the first 3 derivatives is ensured, and the first 3 derivatives at the endpoints can be constrained to any desired value. Trigonometric splines are computationally less expensive than algebraic splines, because there is no need to solve a set of simultaneous linear equations. The derivatives of a trigonometric spline are generally much lower than the derivatives of the corresponding algebraic spline. Trigonometric polynomials are very smooth functions due to the orthogonality of cosine and sine terms.