Bob,
Each BusinessObject has a FillDataSet method that accepts a DataSet as its first parameter:

//Maybe need GetEmptyDataSet() if you haven't 
//  already retrieved any data for this object.
DataSet ds1 = YourBizObj.GetCurrentDataSet();
YourBizObj.FillDataSet(ds1, FirstTableName, SQLCommandString);
YourBizObj.FillDataSet(ds1, SecondTableName, SQLCommandString);

This way you can use one DataSet to store all your tables, including lookups. This is especially desirable if you plan to use DataRelations.

Hope that helps,
---J

>I am evaluating the MM.NET Framework, so I do not have access to the source code. Without an example or detailed documentation it has been difficult. My stumbling block now is how to query two separate tables in the business object without having two datasets.