Studies of the physical properties and diagenesis of biogenous ooze are complicated by the hollow nature of the tests making up the sediment. Established relationships between porosity and other physical properties can be misleading when significant amounts of intratest water are present. If the internal void volumes of biogenous particles are known, total sediment porosity can be corrected for the "excess" water. Previously, only a few estimates of the fraction of total sediment porosity attributable to hollow tests were available. This paper documents direct and indirect measurements which indicate that average intratest void volume in foraminifera decreases from 73 percent to 61 percent as test diameter decreases from 0 to 4 phi units. These internal voids can increase total sediment porosity by 44 percentage points at test diameters of 0 phi, and by 35 percentage points at diameters of 4 phi .