Listening tests were conducted to examine the influence of source spectrum and loudspeaker azimuth on the accuracy of vertical amplitude panning. Subjects judged the perceived elevation of the phantom images created using vertical loudspeaker pairs placed at 0°and 30° azimuths. Six sound sources with different spectral characteristics were used: broadband, low-passed and high-passed pink noises as well as speech, bird and tank shot recordings. Results generally indicated that the localization accuracy was poor, however, lower or upper response biases observed in the results were found to be significantly dependent on the target panning angle, the stimuli and the loudspeaker azimuth angle. In particular, the low-passed noise presented from the loudspeakers at 30° azimuth was perceived to be significantly elevated.