Arachidonic acid (AA) can be metabolised by various enzymes, most notably the cyclooxygenases and the lipoxygenases. The secondary messenger pathway leads to the formation of mediators that are implicated in pathologies such as asthma, inflammation and cancer. Leukotrienes (LTs) are produced through the lipoxygenase pathway. The observation that modulation of leukotriene production by inhibition of 5-lipoxygenase (5-LOX) leads to therapeutic benefit has encouraged research of potent 5-LOX inhibitors. As a consequence, many patents concerning 5-LOX inhibition and the uses of 5-LOX inhibitors as therapeutic agents are claimed each year. This article reviews these patents for the period 1999-2002.