The main objective of this study was to quantify ammonia emissions from organically raised pregnant sows and to compare them with emissions from conventional pig production. A second objective was to quantify the nutrients deposited in the paddock in organic pig grazing systems. Measurements were carried out on three Dutch farms on 1 day in each of two measuring seasons (spring/summer and autumn). Ammonia emissions were measured by the ventilated chamber technique at different locations inside the building and on the paved outside yard. The nutrient loads of N, P and K were calculated according to their content in urine and faeces, average weight of urine and faeces per excretion, and number of urinations and defecations in the paddock. Ammonia emission per m2 did not differ statistically significantly between seasons and between inside and outside the building. Fouling of the floor with urine and faeces had a strong effect on ammonia emission (probability Po0
001). Emissions varied greatly between farms. When emissions were calculated per kg per pig place per year, on one farm they far exceeded the Dutch standard for regular pig farming. On the other two farms they slightly exceeded the standard. The main reason seems to be that pregnant sows on organic farms have outside yards, which are an additional source of ammonia emission. The nitrogen and phosphorus loads on the paddock varied greatly between the farms, statistically significant for N ðPo0
01Þ; not significant for P and significant for K ðPo0
05Þ: The total amount of nutrients on one of the farms (407
5kg ha1 yr1 for N and 113 kg ha1 yr1 for P) far exceeded the permitted levels (170 kg ha1 yr1 for N and 44 kg ha1 yr1 for P)