We calculate the ring rate of the quadratic integrate-and-re neuron in response to a colored noise input current. Such an input current is a good approximation to the noise due to the random bombardment of spikes, with the correlation time of the noise corresponding to the decay time of the synapses. The key parameter that determines the ring rate is the ratio of the correlation time of the colored noise, ¿ s , to the neuronal time constant, ¿ m . We calculate the ring rate exactly in two limits: when the ratio, ¿ s =¿ m , goes to zero (white noise) and when it goes to in nity. The correction to the short correlation time limit is O.¿ s =¿ m /, which is qualitatively different from that of the leaky integrate-and-re neuron, where the correction is O.The difference is due to the different boundary conditions of the probability density function of the membrane potential of the neuron at ring threshold. The correction to the long correlation time limit is O.¿ m =¿ s /. By combining the short and long correlation time limits, we derive an expression that provides a good approximation to the ring rate over the whole range of ¿ s =¿ m in the suprathreshold regimethat is, in a regime in which the average current is suf cient to make the cell re. In the subthreshold regime, the expression breaks down somewhat when ¿ s becomes large compared to ¿ m .