Different methods for the interpolation of head-related transfer functions (HRTFs) were compared. Time domain representations (FIR coefficients) and frequency domain representations (discrete Fourier transform of the impulse response) of an HRTF catalogue were interpolated with the inverse-distance weighting method and the spherical spline method. The interpolated transfer functions were either compared with regard to numerical errors or to differences in perceived quality. In general the errors seem to be larger for time domain representations. Best results were achieved with spherical spline interpolation in the frequency domain.