Sick Building Syndrome (SBS) has been described and even defined as a condition that lacks clinical signs and that abates immediately in those affected after exposure ceases. There is, however, little scientific support for this standpoint. Fatigue, plus symptoms affecting the eyes, nose and skin are frequently reported by those using buildings with indoor air quality problems. Clinical studies have demonstrated a convincing association between reported symptoms and observed signs, especially those associated with the eyes, but there are also clinical signs associated with skin and nasal symptoms. The diagnostic value of laboratory investigations should be further evaluated. Contrary to assertions that SBS symptoms abate shortly after exposure ceases, there are a number of studies showing that a proportion of those exposed to unsatisfactory indoor air quality develop long-term symptoms. There is a need for both an improved definition of the syndrome and further studies of its symptoms and signs.