Eighth Mississippi State - UAB Conference on Differential Equations and Computational Simulations. Electron. J. Diff. Eqns., Conference 19 (2010), pp. 123-133. Title: First integrals for the Duffing-van der Pol type oscillator Authors: Guangyue Gao (Univ. of Texas-Pan American, Edinburg, TX, USA) Zhaosheng Feng (Univ. of Texas-Pan American, Edinburg, TX, USA) Abstract: In this article, under certain parametric conditions, we study the first integrals of the Duffing-van der Pol-type oscillator equations which include the van der Pol and the Duffing oscillator systems, as particular cases. After making a series of variable transformations and applying the Preller-Singer method, we find the first integrals of the simplified equations without complicated calculations. Through the inverse transformations we obtain the first integrals of the original equations. Some statements in the literature are indicated and clarified. Published September 25, 2010. Math Subject Classifications: 34A25, 34L30. Key Words: First integral; Duffing oscillator; van der Pol oscillator; Preller-Singer method; parametric solution.