Marcia, Thanks for your reply.

I am not sure if the problem is due to format the data is stored in these datetime fields in FoxPro and/or MySQL. However, after I retrieve the data from MySQL (using SQLEXEC()), these fields are not NULL. (In fact, none of the fields in my FoxPro table can accept NULL values.) So, the data in these fields is empty (and not NULL). Therefore, even the code with NVL() returns .F.

?NVL( SQLResult.ProcDT, {} ) = NVL( iol_act.ProcDT, {} )  
.F. 
*
* TTOC still returns .T. 
?TTOC(NVL( SQLResult.ProcDT, {} )) = TTOC(NVL( iol_act.ProcDT, {} ))
.T.

At present, I am using TTOC() to convert DateTime field before comparision, and it seems to be working with empty as well as not empty datetime values.