Aim To evaluate the efficacy of ultrasound as a first-line investigation in patients with a clinical soft-tissue mass. Methods Three hundred and fifty-eight consecutive patients (155 male, 203 female, mean age 48 years) referred from primary and secondary care with soft-tissue masses underwent ultrasound evaluation. Five radiologists performed ultrasound using a 10–15 MHz linear transducer and recorded the referrer diagnosis, history, lesion size, anatomical location and depth, internal echogenicity, external margins (well-defined rim or infiltrative), and vascularity on power Doppler (absent or present, if present the pattern was listed as either linear or disorganized). A provisional ultrasound diagnosis was made using one of eight categories. Benign categories (categories 1–5) were referred back to a non-sarcoma specialist or original referrer for observation. Indeterminate or possible sarcomas (categories 6–8) were referred for magnetic resonance imaging (MRI) within 14 days. Additionally category 8 lesions were referred to the regional sarcoma service. Institutional and regional database follow-up was performed. Results Two hundred and eighty-four of the 358 (79%) lesions were classified as benign (categories 1–5). On follow-up 15 of the 284 patients were re-referred but none (284/284) had a malignancy on follow-up (24–30 months). Overall at ultrasound 33 lesions were larger than 5 cm, 42 lesions were deep to deep fascia with 20 showing both features. In this subgroup of 95 patients there were six malignant tumours with the rest benign. Seventy-three of the 358 patients underwent MRI; the results of which indicated that there were 60 benign or non-tumours, 10 possible sarcomas, and three indeterminate lesions. Overall six of 12 (6/358, 1.68% of total patients) lesions deemed to represent possible sarcomas on imaging were sarcomas. Conclusion Ultrasound is an effective diagnostic triage tool for the evaluation of soft-tissue masses referred from primary care.