Analysis of the effectiveness of pressure-reducing seat cushions. Literature review. Investigation of the literature yielded 8 relevant studies. These studies encompassed three clinical trials with a total of 296 patients, and five laboratory experiments with a total of 107 subjects, including patients. The publications were written at level A (RCT and meta-analysis) and level B (other study forms) according to the principles of evidence-based medicine. Both the pressure parameters of the pressure-reducing seat cushion and the development of pressure ulcers were used as measures for outcome. A 7.6 cm foam cushion was used as reference; it was not considered as one of the pressure-reducing systems. Two studies compared different types of air seat cushions with a foam/gel seat cushion. The best distribution of pressure was found for the air compartment seat cushion. This type of seat cushion provided the smallest contact surface with high pressures. Three studies compared the pressure-reducing systems with a 7.6 cm foam cushion. The methodologically most solid one of these three studies found a lower incidence of sitting-related pressure ulcers for users of a pressure-reducing system (0.9 vs. 6.7%; p = 0.04). The two other studies had too low a power to show significant differences. These two compared different types of foam/gel seat cushions and a low profile air seat cushion and found no significant differences in distribution of pressures. One study compared various foam cushions of differing thickness and found that foam cushions most optimally distributed pressure at a thickness of 8 centimetres. Pressure-reducing systems are effective in preventing pressure ulcers. Within the group of pressure-reducing systems, the air compartment seat cushion has the best pressure-distributing properties.