BACKGROUND Sacroiliitis is an important feature of several spondyloarthropathies. While findings on conventional radiographs are delayed, the cost and availability of MRI are still important negative factors. The objectives of the study were-1) to evaluate the role of ultrasound and colour doppler (CD) in the detection of sacroiliitis and 2) to compare these findings with those of normal age matched population. MATERIALS AND METHODS In this prospective study, bilateral sacroiliac joints of 25 patients with suspected sacroiliitis were studied. Radiographs were taken for all patients. MRI was performed for patients with normal or unilateral disease on radiographs. USG and CD were performed for bilateral SI joints. Presence of fluid, echogenic joint space, hypervascularity and low-resistance flow (<0.7) were considered as USG features of sacroiliitis. RESULTS The mean age of the test population was 30.84 years with 76% males, compared to a mean age of 31 years and 81% males in control group. The most common presenting complaint was low back ache with a mean duration of 2.997 years (S.D. 2.17). On grey scale, the width of the diseased SI joint was statistically wider than the control group with fluid seen in 44% of 50 joints evaluated. 88% of the 50 joints were hyperechoic. On CDUS vascularity was identified in 68% with RI values of ≥0.4 to <0.7 in 70% of joints. In the control group, vascularity (at least 2 foci) was identified in 32% joints. However, none showed RI values of <0.7. CONCLUSION Features of inflammation within and around the sacroiliac joints on grey scale were identified as joint widening, increased echogenicity with fluid and on CD as low resistance vascularity patterns. Radiographically negative but MRI positive cases also showed positive CDUS findings, suggesting increased sensitivity. Thus, USG with CD of the sacroiliac joints can prove to be an adjunct to the clinical examination and may be used as an alternative to MRI, when it is not available or feasible.