Reg expressions

Hi,
I would like to grep for a string within a tag, can someone provide some assistance in how to do it? So I would like to use the grep command to find a string like:

<tag>sometext<tag>

because the sometext can be any number of characters or an type of number or lettering, what expression is best to use?

Thanks

If its relatively simple:

egrep "<tag>.*<tag>"

may well work.