A workaround is to use the ClientTemplate and change the strings manually with some JavaScript (http://www.telerik.com/help/aspnet-ajax/htmlchart-client-templates-for-tooltips-and-labels-execute-javascript-and-display-html.html), e.g.: <telerik:RadHtmlChart runat="server" ID="RadHtmlChart1" Width="400px" Height="400px"> <PlotArea> <Series> <telerik:BarSeries> <LabelsAppearance> <ClientTemplate> #if (value > 0) {# $#=value# #} else {# -$#=value * -1# #} # </ClientTemplate> </LabelsAppearance> <SeriesItems> <telerik:CategorySeriesItem Y="20" /> <telerik:CategorySeriesItem Y="10" /> <telerik:CategorySeriesItem Y="-30" /> </SeriesItems> </telerik:BarSeries> </Series> </PlotArea> </telerik:RadHtmlChart>