Foam mattress quality affects pressure ulcer risk but no reliable method to assess mattress fatigue and indentation is available. To ascertain Indentation Quality values of standard 14-cm (5-inch) foam mattresses after 15 years of use, a convenience sample of 50 visco-elastic foam mattresses from a total of 1,000 same-brand mattresses used in a Dutch University hospital was tested using a durometer. Indentation Quality values were obtained on the mattress cover at a relatively unloaded zone (corner), at the head and heel zones, the knee and shoulder areas, and in the middle (buttocks area). Indentation Quality values ranged from a mean of -11.91 mm (+/-2.58) in the unloaded zone to a mean of -26.96 mm (+/-4.31) in the middle zone (buttocks area, P <0.001 compared to all other mattress areas). The value at the relatively unloaded zone was significantly and positively related to the values at the head and the heel zones (r = .70, P <.01) and the knee and the shoulder zones (r = .33, P <.05). The value at the buttocks zone was positively related to the value at the knee and the shoulder zones (r = .35, P <.05). The study showed that mattresses that appeared similar had a wide range of indentation values (indicating a need for individual assessments to monitor their quality) and that Indentation Quality values, determined using the durometer, facilitate objective and quantifiable mattress assessments. Consideration of the consequences of foam mattress life span on quality of care, hospital management practices, and cost analysis is justified.