Pure cultures of Corticium bicolor, Cenococcum graniforme, Rhizopogon roseolus, and Suillus cothurnatus were transported to Puerto Rico in a peat moss-vermiculite medium. Nonmycorrhizal seedlings of Pinus caribaea were inoculated with pure culture or with soil from a pine nursery. Additional non-mycorrhizal seedlings were fertilized. In field and nursery plantings, mycorrhizal seedlings grew better than nonmycorrhizal seedlings. Fertilizer applications did not offset stunting in nonmycorrhizal seedlings. Nonmycorrhizal roots apparently were not invaded by other organisms. Cenococcum graniforme did not colonize pine roots in Puerto Rico. Soil from plantations was very effective inoculum. Two nonsporulating fungi were isolated from previously established pine mycorrhizae, and one subsequently formed mycorrhizae in axenic culture. Forest Sci. 17:239-245.