High-frequency sonar measurements of target strength due to microbubbles were obtained within the wakes of three oceanographic vessels. Two self-contained, high-frequency acoustics instruments suspended at 25-m depth were used to measure the wake acoustic properties during three separate sea trials. The backscatter cross section per unit volume, Mv, as a function of depth and time was calculated from the echo intensity of six upward-looking, conical beam sonars (28–400 kHz). Four 100-kHz steerable sidescans allowed measurement of wake locations, widths, and persistence. In the near-surface core of the wake Mv reached peak values of approximately 0.3 m−1 for the 120- and 200-kHz sonars. The volumetric scattering cross sections were observed to be roughly constant at all frequencies within the top 5–6 m of the wake, suggesting a roughly homogeneous vertical bubble distribution. However, differences in the volumetric backscatter at different acoustical frequencies suggest a higher relative concentration of larger bubbles (≳100 μm) in the center of the wake. The ship wakes were observed to spread to typical widths of up to 66 m (ship speed 10 kn) and to depths of 7–12 m and to persist as strong acoustic scatterers for approximately 7.5 min. Gas diffusion causing bubble dissolution is suggested as the mechanism for decay of the wake bubble clouds.