Search for the pentaquark and H dibaryon

The pentaquark is described as a doublet of states: P⁰ = |c̄suud〉 and P^- = |c̄sddu〉. The H dibaryon is described as: H = |uuddss). Both were predicted to be stable against strong decay or slightly unbound resonances. The considerations leading to these expectations are reviewed. The main properties of these particles: masses, decay modes, life-times and hadroproduction cross sections are discussed. Experimental efforts to search for these particles are reviewed. The search for the pentaquark and the H in the framework of Fermilab E791 is described and preliminary results on the P⁰ → øπp decay mode are presented.