Shoulder ulcers (shoulder lesions) in sows are most commonly observed in the first weeks of lactation, following farrowing. The prevalence of this problem varies greatly from herd to herd due to a range of contributing factors such as management, housing, genetics, health status, history of previous sores and body condition. Shoulder ulcers represent a significant welfare and economic concern to producers. These sores, much like human bedsores, are a form of pressure ulcer and are caused by persistent and constant compression of the blood vessels around the shoulder blade during prolonged periods of lying. The lack of blood flow to tissues results in localized cell death, tissue breakdown, and subsequent ulceration. The prevention of pressure ulcers is of great importance and although many factors have been implicated, maintaining sows in optimum body condition appears to be one of the most significant factors. While research on the occurrence of lesions is limited, their prevalence may be increased in hot climates as sows may spend more time lying, and the presence of moisture (eg. from drip cooling) is known to contribute to ulcer formation. Early signs of redness or irritation should be monitored closely in the farrowing room, as early detection and treatment are needed to prevent shoulder sores from progressing. Once the lesion has developed to include the superficial layers and underlying fat and muscle, the likelihood of recurrence increases greatly. When shoulder lesions appear, the sow should be immediately provided with a soft lying surface such as rubber flooring or deep straw. As the lesions typically occur in the weeks following farrowing, it is often necessary to provide rubber mats directly to sows in farrowing crates, or to wean early and transfer sows to a comfort pen. Measures are also needed to keep sows cool and to encourage movement. Lesions should be cleaned and treated with topical antibiotic. In severe instances, sows should be euthanized. Sows which have suffered from shoulder ulcers in a previous lactation are more likely to develop them in following parities. This is of particular importance when selecting gilt replacements as susceptibility is known to be a heritable trait. If ulcers are observed, then the incidence and animals involved should be recorded to monitor change and effectiveness of treatment, and as an indicator of sow welfare within the herd. The majority of recent research on shoulder lesions has been done in Europe. Further research is needed on risk factors, prevention and treatment under North American farm conditions and genetics.