The Kilifi Developmental Inventory (KDI) is a tool developed in Kenya for the assessment of psychomotor development in infants and young children. We developed age-appropriate standards against which the developmental progress of individual children could be tracked. The current report is based on three studies completed among 1428 children aged between 5 and 36 months and living within rural and urban locations at the Coast of Kenya. We identified age-appropriate cut-offs and expected ranges of performance to facilitate the identification and monitoring of children with impaired psychomotor development.