When you query the SharePoint Search Service the number of rows returned defaults to 100 but can be increased as required.
Note that when you specify a value above the maximum RowLimit the query will only return the default value of 100 items !
ServerContext ctx = ServerContext.Default;
FullTextSqlQuery query = new FullTextSqlQuery(ctx);
query.QueryText = BuildQuery();
query.ResultTypes = ResultType.RelevantResults;
query.RowLimit = 1000;
ResultTable resultTable = query.Execute()[ResultType.RelevantResults];
After some trial and error I found the maximum value for the RowLimit to be 917728059.
query.RowLimit = 917728059;
So don't go around setting the RowLimit to int.MaxValue like I did because this only returns 100 items...
This only applies to the the MOSS 2007 RTM version and seems to be fixed since Service Pack 1.
You can now set the RowLimit to anything from 1 to int.MaxValue and it will return the correct number of items.