Background: The Multidimensional Assessment Pain Scale (MAPS), was developed to measure postoperative pain in critically ill preverbal children. Following preliminary psychometric testing, additional validation of this 5-category 10-point scale was required. This article reports the results of a follow-up validation study that aimed to evaluate the clinical validity and utility of the MAPS. Methods: The MAPS includes five categories and was tested in response to analgesics in a convenience sample of 19 postoperative critically ill children (94% intubated) aged between 0 and 31 months at a tertiary referral hospital in Western Australia. Convergent and concurrent validity was tested using the MAPS, Faces Legs Activity Cry Consolability (FLACC), and Visual Analog Scale observer (VAS(obs)). Clinical utility of the MAPS was also evaluated. Results: The Multidimensional Assessment Pain Scale scores decreased significantly by four points (40% of total score) after the administration of a potent dose of morphine (P < 0.001). Agreement measurements between MAPS and FLACC and MAPS and VAS(obs) showed that the risk of measurement error was small. Internal consistency of the MAPS would improve if the physiologic item was deleted (Cronbach's alpha 0.79-0.64). However, the actual values of heart rate, systolic, mean, and diastolic arterial pressure were shown to decrease significantly (7-14% decrease) at 15, 30, and 60 min after a potent bolus of morphine (P < 0.001). The MAPS also demonstrated clinical feasibility. Conclusions: This study showed that 'MAPS like FLACC and VAS(obs) decreases similarly following rescue morphine. MAPS-revised can be recommended for clinical application.