A semiconductor memory device includes a command buffer that receives an external command and outputs a first command signal, a clock buffer that receives an external clock signal and outputs a first internal clock signal, a delay measurement and initialization unit that receives the first internal clock signal and a fourth internal clock signal and responsively outputs a second internal clock signal and a plurality of delayed signals corresponding to a delay time between when the external clock signal is input and data is output, a delay locked loop that receives the second internal clock signal and outputs a third internal clock signal and the fourth internal clock signal, a latency signal generation unit that delays the first command signal by a delay time between when the second internal clock signal is input to the delay locked loop and when the third internal clock signal is output from the delay locked loop, and then outputs the delayed first command signal as a latency signal, in response to the second and third internal clock signals and the delayed signals, and a data output buffer that outputs the data in response to the latency signal and the third internal clock signal.