Internally, thebibliography environment uses \chapter*; if you want the bibliography to behave like a section, you can patch the \thebibliography command to use \section* instead of chapter*. To do this, add the following lines to the preamble:
\usepackage{etoolbox}
\patchcmd{\thebibliography}{\chapter*}{\section*}{}{}
A complete example:
\documentclass{report}
\usepackage{etoolbox}
\usepackage{lipsum}% just to generate text for the example
\patchcmd{\thebibliography}{\chapter*}{\section*}{}{}
\begin{document}
\lipsum[1]
\begin{thebibliography}{9}
\bibitem{a} Test A.
\end{thebibliography}
\end{document}

If the biblatex package is used to produce the bibliography, one can use \defbibheading to define a heading using \section*:
\documentclass{report}
\usepackage{lipsum}
\usepackage{biblatex}
\addbibresource{biblatex-examples.bib}
\defbibheading{secbib}[\bibname]{%
\section*{#1}%
\markboth{#1}{#1}}
\begin{document}
\lipsum[1]
\nocite{*}
\printbibliography[heading=secbib]
\end{document}

reportsource code, find the macro placing the bibliography, and use\renewcommandin your preamble to remove the call to\pagebreakor similar. – T. Verron Sep 27 '12 at 04:28