\documentclass[12pt]{article}
\usepackage{amssymb,amsmath,amsthm,amsfonts,amscd}

 \usepackage{graphicx}
 \begin{document}
\begin{figure}
  \centering
  \includegraphics[scale=0.5]{fig1.eps}
  \caption{this is a test}
\end{figure} 

\begin{figure}
  \centering
  \special{psfile=fig2.eps scale=0.5}
  \caption{this is a test}
\end{figure}
\end{document}