Animal welfare improves productivity, but has also been increasingly demanded by the consumer. Having a reliable Quality Assurance Scheme based on on-farm welfare audits allows governments to enforce legislation, producers to objectively monitor conditions, and marketers to inform consumers on the animal welfare for specific products. Welfare requirements can be based on natural living, which bases welfare on the type of production system used, or biological functioning, which focuses more on the animal health. The Five Freedoms are UK welfare guidelines, and introduce mental welfare through requiring freedom from fear and stress, and to express natural behaviour. Practical welfare audits need to be performed quickly, and may not always be able to incorporate complex mental welfare assessments. Direct animal-based, and indirect resource-based measures are mainly used in actual audits. Some of the indirect measures taken in an audit are the feeders and drinkers per pig, air temperature, minimum space allowance, and pharmaceutical use. Some of the direct measures commonly used are body condition scores and skin lesion scores for a sample of the herd. Freedom to express normal behaviour is a hard welfare requirement to measure. The presence of vices and stereotyped behaviour can indicate it is not being met, and the need for environmental enrichment is starting to be recognized. QA schemes are now a requirement for the UK market, but specialized QA schemes, like Freedom Food introduced by the RSPCA, have additional welfare requirements. The EU has recently developed a new welfare project that includes focus on animal-based measures, and it is currently in a pilot-stage. Good welfare standards benefit everyone in the industry, and on-farm audits are useful to assess animal welfare.