This study evaluated a 0.0584% hydrocortisone aceponate (HCA) spray (Cortavance; Virbac SA, Carros, France) in canine atopic dermatitis (AD). Initially, dogs with a canine AD extent and severity index (CADESI-03) >or= 50 were randomly allocated to receive HCA (n = 15) or placebo (n = 13) (two sprays from 10 cm away to treat an area of 100 cm(2)) once daily for 28 days. Twenty-one of the dogs then received HCA spray once daily, reducing to every other day or twice weekly over 42 days if improvement was maintained. CADESI, pruritus (14 cm visual-analogue-scale) and owner satisfaction (5-point scale) were recorded every 14 days. Haematology, biochemistry and adrenocorticotrophic hormone stimulation were performed at baseline, d28 and d70 (HCA n = 9; placebo n = 7). Intention-to-treat data were analysed. HCA spray significantly decreased CADESI (-61.4% versus -13.4%, P = 0.0069) and pruritus (-38.8% versus +57.6%, P = 0.0015) at d28 compared to placebo. Scores were significantly decreased at d14 (CADESI -50.5%, P < 0.0021) and d28 (CADESI P < 0.0001; pruritus P = 0.018) compared to baseline following HCA but not placebo. At d28 11 of 15 and 7 of 15 HCA dogs had >or= 50% reductions in CADESI and pruritus compared to 3 of 13 (P = 0.02) and 1 of 13 (P = 0.04) placebo dogs. Owner satisfaction scores were significantly higher in the HCA group (d28 P = 0.0001). Daily 3 of the 21 dogs required daily maintenance therapy, 7 every other day, 6 twice weekly and 5 dogs required additional therapy. Coat length did not influence the results. No adverse effects or changes to blood parameters were noted. HCA spray proved safe and effective up to 70 days. It is not, however, licensed for long-term treatment.