In this work, speech signal having information up to 4 kHz is termed as narrowband (NB) speech and the other having information up to 8 kHz is termed as wideband (WB) speech. The objective is to demonstrate the significance of speaker information present in the WB speech. A speaker verification (SV) system is developed using the mel-frequency cepstral coefficients (MFCCs) computed from the WB speech and modeled using Gaussian mixture models (GMM). For comparison, a SV system is also developed from the corresponding NB speech. The experimental results show that the SV performance improves for WB speech and the improvement is significant under degraded conditions. Further, the performance improvement is better for female speakers. © 2011 IEEE.