A 44-year old West-African living in Germany since 18 years presented because of persistent painful swelling of both ankle joints and diffuse lymphoedema of feet occurring after a trip to Morocco. Laboratory tests revealed inflammation and eosinophilia. HLA-B27 was positive. Antinuclear antibodies and rheuma factors were not found. There was no evidence of an infection with bacteria or viruses known to cause arthritis. Filariasis was excluded. Microscopy of fresh stool revealed larvae of Strongyloides stercoralis. Symptoms resolved after specific antihelminthic therapy with ivermectin 0.2 mg kg(-1) day(-1) for 2 days and non-steroidal anti-inflammatorials. Reactive arthritis is known to be caused by various bacterial agents. In some individuals, arthritis may be due to helminths, such as S. stercoralis. Patients with strongyloidiasis may respond to non-steroidal anti-inflammatorials but must not undergo treatment with corticosteroids before having received antihelminthic therapy because immunosuppression may result in life-threatening strongyloides hyperinfection syndrome.