Forty-eight two-month-old guava (Psidium guajava L. var. Kampuchea) seedlings given three levels of a biological soil conditioner (BSC) were tested in greenhouse studies for their response to vesicular-arbuscular mycorrhizal fungi. Dry weighs of shoot, root, and dry matter (DM) yield of uninoculated seedlings increased with increasing levels of BSC. In contrast, mycorrhizal plants attained maximum DM yield at lower levels of BSC. Levels of BSC significantly influenced mycorrhizal dependency (MD).