CYP2D6*142 is assigned uncertain function based on inadequate evidence. A subject sequenced as CYP2D6*10/*142 had a risperidone/9-hydroxy-risperidone ratio comparable to subjects with an AS of 0.25, 0.5 or 0.75 (33998274). CYP2D6*142 is a rare allele defined by several SNPs including 100C>T which causes decreased function in other CYP2D6 alleles (e.g. *10). Therefore, consensus among experts was uncertain function.