Edit
After researching this problem a bit more it appears Visual Studio doesn't support Markup as HTML for rdlc
reports until Visual Studio 2010. So if upgrading is an option, then you can do what you want.
Otherwise you could always just strip out the HTML tags like so:
On the Report
menu, click Report Properties...
and select the Code
tab. Enter the following code:
Function StripHTMLTags(ByVal text as String) AS String
Return System.Text.RegularExpressions.Regex.Replace(text, "<(.|\n)*?>", "")
End Function
Now in your cell use the following expression:
=Code.StripHTMLTags(Fields!MyField.Value)
Original answer follows:
Leaving aside that you should separate data from presentation, you can render using HTML tags in Reporting Services, its just not very intuitive to find:
- Left click the field you want to display so that the
<Expr>
tag is highlighted
- Right click the highlighted
<Expr>
tag and choose Placeholder Properties...
- On the
General
tab, select the HTML- Interpret HTML tags as style
radio button
Only a limited number of tags are supported however. This article on MSDN tells your more.
Screenshots:

