Hi, I'm afraid that negative index subscripting in IDL can't be disabled. Also, you may already be aware but the STRICTARRSUBS setting to COMPILE_OPT only applies to array subscripting but not scalar index subscripting. This is mentioned in the IDL Help under the Contents section: Language > Arrays > Using Arrays as Array Subscripts or on the Exelis VIS web site Documentation Center: http://www.exelisvis.com/docs/Using_A... under the sub-sections: Array Subscripts and Clipping Negative Indices versus Array Subscripts I'm sorry I don't have better news. Regards, Jim Exelis VIS