Fear of loud noises is a common welfare problem in pet dogs. Commercial treatment vests have been tested on dogs to relieve noise phobia, and peripheral oxytocin has been suggested to be one of the stressrelieving mediators. The effect of vests has not, however, been tested in a controlled situation. We tested whether individually customized vests, have an effect on behaviour of severely noise phobic dogs in a double-blinded experiment, where dogs are exposed to loud noises. We also investigated the possible effect of pressure by using two types of vests; a deep pressure vest (DEEP, c. 10-12 mmHg) and a light pressure vest (LIGHT, c. 2-3 mmHg). In addition to behaviour, we studied if the pressure vest has an effect on urine oxytocin level and on saliva cortisol levels. A total of 28 dogs (2-11 years), both female (18) and male (10), were recruited via an ongoing study on the genetic background of noise sensitivity by the Finnish Canine Genetic Research Group. Each dog was tested three times either without vest (CONTROL) or with DEEP or LIGHT vests in a semi-randomized order. The dogsí behaviour was video recorded for 6 min, including three 2 min intervals: pre-noise, noise (70-73 dB firework sound) and recovery. Behavioural parameters included activity, body and tail postures, vocalization, and time spent near owner. Saliva samples were collected twice before and twice after the noise test. Urine samples for oxytocin analyses were collected when the deep pressure vest was first fitted: before dressing the dog and 30 min later. The DEEP vest reduced the lying time of the dogs during the noise interval. During the noise interval total lying time with any vest correlated positively with saliva cortisol, measured after noise interval, indicating that the increased lying time was a sign of a higher stress level in the dogs. Wearing either vests increased the time the dogs spent near their owners during noise interval. Time spent near the owner when wearing the DEEP vest during the recovery interval correlated positively with the urine oxytocin. These results indicate oxytocin might be related to the dogís tendency to seek owner support and the vests might effect this behaviour positively. We did not find a clear therapeutic effect of using pressure vests in noise phobic dogs. However, our results indicate the pressure vest might reduce the acute stress reaction and speed up the recovery after stress.