Synchronous activity among synaptically connected interneurons is thought to organize temporal patterns such as gamma and theta rhythms in cortical circuits. Interactions between distinct interneuron circuits may underlie more complex patterns, such as nested rhythms. Here, we demonstrate such an interaction between two groups of CA1 interneurons, GABA_A,slow and GABA_A,fast cells, that may contribute to theta and gamma rhythms, respectively. Stratum lacunosum-moleculare (SL-M) stimuli that activate GABA_A,slow inhibitory postsynaptic currents (IPSCs) in pyramidal cells simultaneously depress the rate and amplitude of spontaneous GABA_A,fast IPSCs for several hundred milliseconds. This suppression has a similar pharmacological profile to GABA_A,slow IPSCs, and SL-M stimuli elicit GABA_A,slow IPSCs in interneurons. We conclude that GABA_A,slow cells inhibit both pyramidal cells and GABA_A,fast interneurons and postulate that this interaction contributes to nested theta/gamma rhythms in hippocampus.