OBJECTIVES: To validate the modification of the prolonged Papanicolaou stain based on the quality control of time, units and staining stages (micro- and macroscopic), and on the stain reactivation based on the control. STUDY DESIGN: A prospective study was performed on 125,358 cervical smears in Lima (Peru). The microscopic quality control included evaluating the cytological characteristics through the staining quality index (SQI) and the quality criteria for samples described by the Bethesda System (TBS). The macroscopic quality control is based on the interslide staining as a set corresponding to a poststaining vertical angle. The stains were reactivated with the addition of 0.15 and 2 g of phosphotungstic acid for Orange G and EA-50, respectively. RESULTS: Both the nonneoplastic and the neoplastic findings comply with the quality criteria of the TBS (SQI value = 0.94). The yield per battery of staining fluctuated between 5,616 and 17,954 Pap smears, and the reactivation of stains produced a stain yield of up to four times the initial amount of the smears, saving USD 5,598.88 from 2013 to 2014. CONCLUSION: The modification of prolonged Papanicolaou staining is an excellent alternative, with a cost-benefit ratio that generates savings and a higher yield per battery of staining.