Pentaquarks

I discuss the recent experimental and theoretical developments following the discovery of the Θ⁺ pentaquark - an exotic uudds̄ baryon resonance observed by several experiments, and Ξ^{* -} (ddssū) reported by NA49. I focus on the theoretical interpretation of the data, on the predictions for related exotic states, and on several unresolved questions: Why some experiments observe the pentaquarks and others do not, the apparently extremely narrow width of the Θ⁺, and the determination of its parity. I also discuss the proposed heavy-quark pentaquarks - Θ_c (uuddc̄) and Θ_b ⁺ (uuddb̄), which are expected to be extremely narrow or even stable against strong decays. H1 recently reported the observation of a possible Θ _c candidate in D ^*- p channel. Pentaquarks are also being searched for in e ⁺ e ^- and γγ in the LEP data and at B-factories.