Introduction: Mycoplasma (M.) hyorhinis is ubiquitous within the swine population and can be detected in both, healthy and diseased animals. It is considered a normal member of the bacterial flora of the upper respirator), tract of young pigs. The pathogenicity of the bacterium is yet discussed, but M. hyorhinis is described to cause pneumonia and polyserositis in pigs. The objective of this survey was to investigate the effects of tulathromycin (Draxxin(R), Fa. Pfizer Tiergesundheit) against M. hyorhinis in growing pigs in a field trial. Materials and Methods: This study included 150 pigs starting off with an average bodyweight (bw) of 18 kilogram (kg). They were randomly divided into a treatment and a control group. Pigs of the treatment group received a single dose of 2.5 mg tulathromycin/kg bw intramuscularly on study day (ST) 0. During the study pigs were individually weighed (ST 0, 15) and a cough index was calculated for each group (ST 0, 1, 2, 3, 5, 7, 9, 11, 13, 15). Thirty pigs from each group were selected for further clinical examination on ST 0, 5 and 15. On the same STs bronchoalveolar lavage fluid samples (BALF) were collected from these 60 animals. Pigs were anaesthetized with ketamine (20 mg/kg bw) and azaperone (2 mg/kg bw) for BALF sampling. The BALE was analysed for M. hyorhinis by PCR and culture. Results and Discussion: The percentage of positive animals and the amount of M. hyorhinis detected on ST 0 does not differ significantly between the two groups. In both groups a significant reduction of the number of animals positive by PCR is detectable over the study period. Furthermore the amount of M. hyorhinis isolated from BALE is significantly reduced in the treated animals. However, the reduction is more distinctive for treated animals leading to a significant difference between the two groups on ST 5 and 15. The cough index of the treatment group frills constantly from STs 1-9 and stays below the values of the control group over the second half of the study. The clinical score is significantly reduced from ST 0-15 in both groups. From ST 5-15 a significant rise in the clinical score is observed in the control group, while it stays low in the treated animals. Starting off with equivalent mean body weights on ST 0, the average daily weight gain is significantly higher in the treatment group during the trial period. The trial data verifies the positive effect of a single treatment with tulathromycin on the health status and performance of the pigs. In particular; the reduced amount and detection rate of M. hyorhinis in the treatment group prove the efficacy of tulathromycin against this pathogen.