Field trials were conducted in California during 1988 to determine the effects of VA mycorrhizal inoculation on cotton yields. Results showed that inoculation consistently improved yields by 10-20% when cotton was grown on low-phosphorus soils. Further trials conducted during 1989 across the cotton belt appear to corroborate these findings, although results are not yet complete. Commercial VA mycorrhizal inoculants for use in cotton agriculture are under development.