Objective. To compare the efficacy of subcutaneous extralesional triamcinolone acetonide injection versus conservative treatment for chalazion. Design. Randomised controlled trial. Setting. Eye clinics of two regional hospitals in Hong Kong. Patients. Patients over 18 years old presenting with primary chalazion were randomised into two groups. In group 1, 12 patients were treated with lid hygiene, warm compresses, and chloramphenicol 1% ointment 4 times a day. In group 2, 16 patients were treated with 0.3 mL triamcinolone acetonide (10 mg/mL) injection to the subcutaneous tissue extralesionally via the percutaneous route. Exclusion criteria were: acutely infected chalazion with preseptal cellulitis, recurrent chalazion, small chalazion (≤2 mm), and prior treatment to chalazion. Main outcome measures. Size of chalazion, recurrence of chalazion, intraocular pressure, and complications from treatment, including skin pigmentary change or atrophy and pyogenic granuloma.Results. There was a clinically and statistically significant difference between the success rates in group 1 (58.3%) and group 2 (93.8%). In group 1, the mean prior duration of chalazion before treatment was significantly shorter in success cases than in failed cases. One patient with multiple chalazia in group 2 developed hypopigmentary skin changes at one treatment site. Conclusion. Subcutaneous extralesional triamcinolone acetonide injection was more effective than conservative treatment for chalazion.