en Electricity Markets and Regulation Electricity Markets and Regulation Research Paper Research Paper Strategic bidding in joint energy and spinning reserve markets is a challenging task from the viewpoint of generation companies (GenCos). In this paper, the interaction between energy and spinning reserve markets is modeled considering a joint probability density function for the prices of these markets. Considering pay-as-bid pricing mechanism, the bidding problem is formulated and solved as a classic optimization problem. The results show that the contribution of a GenCo in each market strongly depends on its production cost and its level of risk-aversion. Furthermore, if reserve bid acceptance is considered subjected to winning in the energy market, it can affect the strategic bidding behavior. Bidding Strategy,Electricity Market,Energy Market,Spinning Reserve Market,Pay-as-Bid Pricing, 36 43 http://ijeee.iust.ac.ir/browse.php?a_code=A-10-804-1&slc_lang=en&sid=1 H. Rajabi Mashhadi h_mashhadi@um.ac.ir 180031947532846002119 180031947532846002119 Yes Mashhad, IRAN J. Khorasani Javid@bojnourdiau.ac.ir 180031947532846002120 180031947532846002120 No Science and Research Branch, Islamic Azad University, Tehran, Iran