The memo said Sidley Austin's London office also would be downsized, although few details were included, The Chicago Tribune reported.
Citing the global economic downturn, Sidley Austin officials said they were aligning the firm's staffing levels to match the volume of expected work in the next 12 to 18 months. The firm reportedly has more than 1,800 lawyers in 16 offices worldwide.
"A proper alignment of capacity to demand is not just about financial performance," firm officials said in the memo. "It is necessary for keeping all of our personnel fully productive and professionally satisfied -- and for the maintenance of our overall morale and competitive position."