Latex Problem: Undefined control sequence when using /multirow

I simple want to combine some cells in a row of a table in Latex. For instance,
I tried to compile the following table:

\begin{tabular}{|l|l|l|}  
\hline  
\multicolumn{3}{|c|}{Team sheet} \\  
\hline  
Goalkeeper & GK & Paul Robinson \\ \hline  
\multirow{4}{*}{Defenders} & LB & Lucus Radebe \\  
 & DC & Michael Duberry \\  
 & DC & Dominic Matteo \\  
 & RB & Didier Domi \\ \hline  
\multirow{3}{*}{Midfielders} & MC & David Batty \\  
 & MC & Eirik Bakke \\  
 & MC & Jody Morris \\ \hline  
Forward & FW & Jamie McMaster \\ \hline  
\multirow{2}{*}{Strikers} & ST & Alan Smith \\  
 & ST & Mark Viduka \\  
\hline  
\end{tabular}  

Then I get the error:

! Undefined control sequence.  
<recently read> \multirow  

l.821 \multirow

Does anyone have an idea what I am doing wrong? Do I need a special package? Interestingly enough, the multicolumn command is working! Weird.