Thanks Bonnie. The data returned to the UI will be small, so the "chunky" option should be a good choice.

The first version of the software will be an old-style Windows application (all the components except the database will reside on the user computer). This decision is mainly due to the fact that this is my first project in .NET and considering all the things I need to learn and the ridiculy small amount of time I have to complete the project, I don't want to overcomplicate the project.

The second version of the software will have both a Windows and a web front end, so I intend to remove the BO components from the user computer to place them on a server. My next question will be wich method of communication is better between the layers: .NET remoting or web service? Or both (.NET remoting for the WinForms and web services for the web)?

In that context, will the "chunky" option still be relevant or I should go with the "chatty" option instead?

TIA

>This all boils down to the "chatty" vs "chunky" methodologies. Chatty would be many calls to the back-end, chunky would be getting as much as possible in one fell swoop. Typically, chunky is better, unless there's huge amounts of data involved. In this particular example, if you're talking about a lot of data, I might lean towards your first option, one call for each table, since each table is dependent on what the user chooses from the Combos. Again, this all this depends on how large your anticipated data will be.
>
>Another question to think about is whether or not to use Web Services to access your server-side data (I recommend it).