Background: Acute low back pain is a common condition that is encountered by many physicians. Varied treatments are instituted in its management with no defined standard protocol in our institution. Additional physiotherapy has had minimal impact in terms of pain control and the time to return to work in the available literature. Controversy remains regarding effectiveness of ultrasound physiotherapy and its role in management of acute low back pain. Objective: To investigate the effectiveness of the addition of ultrasound physiotherapy to analgesia in patients with acute low back pain at the Aga Khan University Hospital, Nairobi. Methods: A randomized controlled trial was conducted to compare the effect of addition of ultrasound therapy to a defined analgesia protocol in patients presenting with acute low back pain at our institution. The primary outcome was reduction in pain and a secondary outcome of disability was analyzed. Seventy four (74) cases (37 in each arm) were needed to detect a 5 point difference in the Oswestry Disability Index score with a power of 80%. The effect of additional ultrasound on disability and symptom relief was evaluated using the mean change in Oswestry disability index (ODI) and visual analogue scale score for pain (VAS), respectively. Patients were followed up for a minimum of 4 weeks with assessment using the ODI and VAS at weekly clinic visits. Analysis: Data analysis was performed using SPSS version 17.0 and STATA-10 software. Difference in the means was compared using the student t-test and the Mann-Whitney U test to compare non parametric data such as the individual ODI scores. A p-value of <0.05, by convention, was considered to be a statistically significant result. Results: A total of one hundred and eight (108) patients were screened of whom 34 were excluded and 74 were eligible. Thirty six (36) patients were allocated to the analgesia with additional ultrasound group and 38 to the analgesia alone group. There was no difference in the mean change in the ODI score between the two groups at any of the four follow up visits after initiation of treatment. Mean difference in change of ODI (95% confidence interval) was -3.2(-7.0 to 0.6) after the first week, 2.96(-1.3 to 7.2) after the second and 1.90(-2.3 to 6.1) after the third week, p=0.36, 0.17 and 0.096 respectively. There was also no difference detected in the mean change of VAS score in between the two groups at the first and