We have Jasper 4.0 CE version, but I'm pretty positive that it's the same in 4.5 as well. I created Master / Detail reports where from the list of sale records you can select one and open another report with more details about that sale. So the "Detail" report (Drilldown in your case) has the parameter that is NOT required. I say it capital letters because I created another copy of "Detail" report where user can just open it and enter sale id and that one has sale id as required. Another thing, which may be specific to 4.5 as oppose to 4.0 is that I speicified path to "Detail" report without "repo:" prefix. In my case it is "/Source_Code/Subreports/...". It's different when I reference company logo as resource - I put "repo:/Source_Code/Images/...", but NOT for opening another report.