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Exercise areas represent an important component in dairy agriculture and are an hazard of manure dilution, of surface and ground waters pollution and of ammonia emissions (R.J. Croft, 1989). The permanence of manure on free surfaces has, as a consequence, the emission of ammonia in the environment. The present work aimed to evaluate the amount of ammonia losses from these areas in real operating conditions and in different environmental conditions. The production of manure in the exercise areas was investigated taking samples - with a frequency of 5 days - on 12 areas of 1 square metre casually chosen inside a dairy cattle barnyard of the Western Po Valley. Samples of fresh material - liquid and solid fractions of manure - and of material left on the pavement after manure removal were collected and used in the trial for the determination of ammonia losses. The emissions from samples of the three different materials -deposed on a concrete surface- were measured for 80 hours, with three replications. The average manure production, determined in the exercise area, was of 130 gTS/m2.day, with an amount of material near 630 ( 340) g/m2 of pavement -5 days after manure removal- and near 3410 ( 700) g/m2 of pavement -20 days after manure removal. A computer model able to predict the amount of nitrogen losses in relation to manure production, ammonia emissions of the different manure fractions, surface per head in the exercise area and manure removal frequency- was developed. The trial results and the following data processing showed as, in our test conditions, the ammonia loss is ranging from 5 to 20% of the total nitrogen produced in dairy exercise areas depending on manure removal frequency.