Oxime ester compounds of formula (I), wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 independently of each other are hydrogen, C1-C20alkyl, (A), COR14, NO2, or OR15; provided that at least one of R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 is (A), and provided that at least one of the remaining R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 is COR14 or NO2; R11 is for example C1-C20alkyl, M or (B); X and X1 are for example a direct bond; R12 and R′12 are for example hydrogen or C1-C20alkyl; R13 and R′13 are for example C6-C20aryl or C3-C20heteroaryl; M is (X), (Y) or (Z); X3 is O, S or NR19; R14 and R15 are for example phenyl; R20, R21, R22, R23, R24, or R25 for example are hydrogen, COR14, NO2, or (B); provided that at least two oxime ester groups are present in the molecule; are useful as photoinitiators.