>>There are no difference between PRIVATE variables defined in your MAIN program and PUBLIC ones :o)
>>They are visible everywhere.
>
>What about private variables defined in the calling program? Would they be visible in all form's methods? Just to be 100+% sure.

Yes,
If you define a PRIVATE variables in some routine and then call FORM in it all variables defined as PRIVATE there will be visible, but there is a trap there. If the form is not modal the routine ends its job and ALL variables are released. So better store these variables in some properties of the called form or make the form modal :-)