Enhancement of ultrasonic backscatter and reflectivity from tissues has been demonstrated in the past using gas bubbles and thermal effects. This paper presents a new approach, whereby such enhancement can be achieved by the introduction of suitable aqueous solutions into tissue. Ideally, such solutions should exhibit low toxicity and ultrasonic properties markedly different from those of tissue. Twenty-two potential materials were identified and the speed of sound, density and acoustic impedance in their solutions were determined as a function of concentration. Some of these solutions were used in preliminary in vitro and in vivo canine experiments and echo enhancement was demonstrated.