Achieving and maintaining high herd health and welfare status and low veterinary medicine inputs are important aims in organic livestock farming. Therefore, an on-farm intervention study (CORE Organic ANIPLAN) was conducted on 128 organic dairy farms in seven European countries aiming at minimising medicine use through animal health and welfare planning (AHWP). Medicine use (excluding complementary treatments such as homeopathic remedies) was assessed as the total number of treatments and as the number of treatments of various disease categories (udder, fertility, metabolism, locomotion and others) generated from farm records and national databases, respectively. Health and production data were calculated at farm level from milk recording data: Somatic cell score (SCS) was used as an indicator for udder health, incidences of low (<1.1) and high (>1.5) fat-protein ratio as indicators of rumen acidosis and imbalanced energy supply, respectively. Calving interval was used as an indicator for fertility. Milk recording data and treatment data were retrospectively collected for a one year period before and after the first farm visit. Focus areas of animal health and welfare plans were either generated in Stable Schools (adapted Farmer Field Schools) or using face-to-face advice but following similar principles. Most frequently chosen focus areas were metabolic disorders (66% of farms), udder health (58%), lameness (47%), and fertility (39%). General linear models for repeated measures were used to analyse the development at the farm level. The total number of treatments, the number of udder treatments and the number of metabolic treatments were all significantly reduced during the one year study period, whilst the number of treatments of lame cows increased. With the exception of SCS, which improved significantly, the other health indicators remained stable. Milk yield and average lactation number also remained unchanged. Choice of different focus areas had no significant effects on the corresponding treatment and health variables except for indication of rumen acidosis; for the latter situation on farms with an AHWP focus on metabolic issues improved, but this was not the case across all farms. Overall, the implementation of AHWP reduced total treatment incidence and improved the udder health situation across all farms regardless of the focus areas in the AHWP. Hence, AHWP can be regarded as a feasible approach to minimising medicine use without the impairment of production and herd health under several organic dairy farming conditions in Europe. (C) 2012 Elsevier B.V. All rights reserved.