An analysis of wide-beam, Sea Beam and map-count data in the eastern and southern Pacific confirms the hypothesis that the average number of ''ordinary'' seamounts with summit heights h≥H can be approximately by the exponential frequency-size distribution: &ngr;(H)=&ngr;0 e-&bgr;H. The exponential model, characterized by the single scale parameter &bgr;-1 is found to be superior to a power-law (self-similar) model. The exponential model provides a good first-order description of the summit-height distribution over a very broad spectrum of seamount sizes, from slmall cones (h3500 m). The distribution parameters obtained from 157,000 km of wide-beam profiles in the eastern and southern Pacific Ocean are &ngr;0=(5.4¿0.65)¿10-9 m-2 and &bgr;=(3.5¿0.21)¿10-3 m-1, yielding and average of 5400¿650 seamounts per million square kilometers, of which 170¿17 are greater than one kilometer in height. The exponential distribution provides a reference for investigating the populations of not-so-ordinary seamounts, such as those on hotspot swells and near fracture zones, and seamounts in other ocean basins. If we assume that volcano height is determined by a hydraulic heat proportional to the source depth of the magma column, then our observations imply an approximately exponential distribution of source depths. For reasonable values of magma and crustal densities, a volcano with the characteristic height &bgr;-1=285 m has an apparent source depth on the order of the crustal thickness.