The genetic variation of human butyrylcholinesterase has been associated with height, body mass index, Alzheimer's disease, and response to xenobiotic agents. The present study reports four new mutations, found in the exon 2 of the BCHE gene, in a sample from 3001 Brazilian blood donors. The three nonsynonymous mutations and one synonymous mutation detected are: 223G-->C, G75R; 270A-->C, E90 D; 297T-->G, I99 M; 486T-->C, A162 A, respectively. All these variants are rare: 0.093+/-0.093% for the missense mutations and 0.137+/-0.137% for the synonymous mutation. A table with the 58 non-usual variants of butyrylcholinesterase is also presented.