Synopsis This paper describes tests carried out to examine the relationship between ultrasonic pulse velocity and cube strength of concrete from ages of about 3 h over a curing temperature range from 1 to 60°C. It is found that this relationship is practically independent of water/cement ratio and temperature but influenced by both aggregate content and type of cement. Strength estimation from pulse velocity was found to be less reliable for velocities less than about 2 km/s than it is for higher velocities. Prediction of 28 day cube strength from early-age pulse velocity is possible with some limitations, particularly with regard to temperature effects.