An equation of state for homonuclear chain molecules is formulated on the basis of thermodynamic perturbation theory of Wertheim. It yields a very accurate prediction of the compressibility factor of different chain molecules including hard spheres and hard dumbbells as well as flexible chains with up to 200 bonds in a molecule. In addition, a large number of molecular simulation results are used to test the thermodynamic first-order perturbation theory (TPT1), the thermodynamic second-order perturbation theory (TPT2), the scaled particle theory (SPT), the Percus-Yevick and Carnahan-Starling (PY-CS) equation, the generalized Flory-Dimer equation (GF-D) and our equation. For short chain molecules (m less than or equal to 4), good agreement between the calculated and computer simulation data can be obtained from all of the above equations, but for long chain molecules the equation proposed in this work is better than the other equations.