There are several ways:
- Some column headers are much larger than the data in the column, using two or more lines for the header makes smaller column widths.
Use of smaller fonts. For example:
\begingroup
\small
\begin{tabular}...\end{tabular}%
\endgroup
The distance between columns can be made smaller, see example below.
The whole table can put in \resizebox of package graphicx (graphics), e.g.
\resizebox{\linewidth}{% no space
\begin{tabular}...\end{tabular}% no space
}
In your case use \textheight instead of \linewidth.
Caution with spaces by line ends. Inside \resizebox, \rotatebox, … they are set because of horizontal mode, see the comments "no space" in the example above.
The example below uses two lines for some header entries and uses smaller distances between columns.
\documentclass[a4paper,12pt]{report}
\usepackage[pdftex]{graphicx}
\usepackage{booktabs}
\newcommand*{\headtab}[1]{%
\begin{tabular}[t]{@{}l@{}}#1\end{tabular}%
}
\begin{document}
\noindent
\rotatebox{90}{%
% shrinking the distance between columns a little bit
\setlength{\tabcolsep}{.9\tabcolsep}%
\begin{tabular}{cccccccccccc}
\toprule
&&&&&&&&
\multicolumn{4}{c}{%
\textbf{\headtab{\% of structures\\with \boldmath$p$-value $<$ 0.1}}}\\
\midrule
&&&\textbf{\headtab{RMSD\\0.5\,\AA}} &
\textbf{\headtab{RMSD\\25\,\AA}} & \textbf{\boldmath$\delta$ value} &
\textbf{\headtab{p-value\\median}} &
\textbf{\headtab{p-value\\average}} & \textbf{0.5\,\AA} &
\textbf{1.5\,\AA} & \textbf{3.0\,\AA} & \textbf{5.0\,\AA} \\ \midrule
EROS&without
tail&bb&0.78$\pm$0.22&0.60$\pm$0.05&30\%&0.29&3e-9&33\%&53\%&53\%&37\% \\
&&sc&2.00$\pm$0.38&1.42$\pm$0.08&41\%&0.06&$<$2.2e-16&61\%&79\%&74\%&42\%
\\
\end{tabular}%
}
\end{document}

\usepackage[margin=1in]{geometry}and put\footnotesizeafter\rotatebox{90}{. But the fonts will have foot note size though. – Harish Kumar Sep 21 '12 at 0:30