A method was developed for the quantitative determination of two components of soil organic phosphorus. The method involves differential elution of the compounds by dilute hydrochloric acid from a bed of the weak-base anion exchange resin De-Acidite. One component was identified as an inositol hexaphosphate, in which the inositol was probably present as the meso isomer. The other component was less accurately identified. It was suspected to be an isomer of inositol hexaphosphate;The two inositol hexaphosphates made up 16 percent of the organic phosphorus fraction in samples of 49 surface soils. The content ranged from 4 p.p.m. to 98 p.p.m. About two-thirds of the total was meso-inositol hexaphosphate and one-third was the supposed isomer of inositol hexaphosphate. The content of inositol hexaphosphate was positively associated with the content of organic phosphorus in other forms. The regression of inositol hexaphosphate content on the content of other forms, independent of pH and free iron oxide, was significant at the 1 percent level. The content of inositol hexaphosphate was not significantly associated with soil pH and free iron oxide content independently of the content of other forms of organic phosphorus;Some evidence was obtained that the inositol hexaphosphate and the other organic forms of phosphorus do not decompose at different relative rates in soils;Evidence was obtained that soil microorganisms synthesize both meso-inositol hexaphosphate and the supposed isomer of inositol hexaphosphate, as a result of which part of the inositol hexaphosphate in soils appears to be microbially derived;The value of approximately 2 for the ratio of the phosphorus present as meso-inositol hexaphosphate to that present as the supposed isomer in soil organic phosphorus is rather different from the ratio of approximately 0.5 for the same substances in the organic phosphorus produced by soil microorganisms. Since meso-inositol hexaphosphate is found in plants and the supposed isomer apparently is not, it was speculated that most of the meso-inositol hexaphosphate in soils is residual from plants. Some of the meso-inositol hexaphosphate and all the supposed isomer of inositol hexaphosphate are presumably of microbial origin.