There's an article in the March GW mag going through a number of chillies in heat order from gentle giant to blow your head off. Bhut Jolokia is listed as the Guiness world record holder at 1,001,304 SHU. Dorset Naga is listed as 923,000 to 1,598,000 SHU - it reached the higher number in a GW trial in 2006.