Abstract: Several types of infinite integrals involving essential singularities of the integrand in the interval of integration are studied. The integrands are products of a general rational function, a trigonometric function of x and one of 1/x. General formulae are derived by using the approach of contour integration and the results are expressed in terms of residues. Several examples are given.

Key words: infinite integrals, essential singularities, contour integration, residue theorem