The moisture/solute diffusivity,texture and colour of sweet potato pretreated in distilled water with ultrasound (UD),osmotic dehydration without ultrasound (OD) and osmotic dehydration with ultrasound (UOD) were investigated to determine the effects of ultrasound on osmodehydrated sweet potato.The ultrasonic probe of 2 cm diameter,having frequency of 28 kHz and power of 300W was used for the experiment at pretreatment times of 20,30,45 and 60 min.The pulsed on-time and off-time was 10 and 2 s respectively.The osmotic solution was made to circulate counter currently through the experimental set up.