Trinidad and TobagoStudies were undertaken to determine the effects and relationships of compost type, aeration, and brewing time on compost tea properties, phytotoxicity, and efficacy in inhibiting growth of Pythium ultimum in vitro. The effect of compost tea on dry matter of tomato and sweet pepper seedlings cultivated on compost-amended substrate was also investigated. Compost type, aeration, and brewing time significantly affected the microbial and chemical properties of compost teas made from banana leaf (BLC) and lawn clipping (LCC) composts. Both aerated and nonaerated compost teas made from BL and LC composts significantly inhibited mycelial growth of P. ultimum. However, growth inhibition (GI) levels were significantly higher in compost teas produced from LCC. Aerating compost tea (ACT) did not consistently result in higher GI levels across compost types. Neither did increasing brewing time beyond 18 h for ACT and 56 h for nonaerated compost tea (NCT). Across all ACTs, yeast population was positively related to GI whereas bacterial population had a positive relationship with GI across all NCTs. Evidence suggests that multiple groups of microorganisms contributed to GI through antibiosis and competition for resources. All compost teas stimulated seed germination of tomato and root growth in sweet pepper. However, NCTs brewed for 56 h using LCC or BLC, and ACT produced from BLC brewed for 18 h, significantly reduced seed germination of sweet pepper. Application of NCT brewed for 168 h made from BLC significantly increased total dry matter of tomato seedlings by 122% compared with the control.