A questionnaire study was performed in 99 workers at a large sewage treatmentplant to investigate self-reported health complaints from workplace exposure to bioaerosols. The studypopulation was divided into subgroups according to different work stations: mechanical treatment (MT),biological treatment (BT), sewage sludge treatment (SST) and operation control (OC). The questionnaireincluded personal data, workpost and job characteristics, exposure to chemicals, history of employmentand exposure, workplace hygiene and protective measures, smoking and drinking habits. There was alsoa series of 25 questions on subjective health complaints grouped into the following clusters: 'flu-likesymptoms', 'respiratory symptoms', 'nose, eye, throat and skin irritation', 'neurological symptoms' and'gastrointestinal symptoms'. Each subject was asked whether the complaints had occurred 'frequently','rarely', or 'never' within the previous 12 months. Air concentrations of endotoxins and (1 --> 3)- beta-D-glucansin the worker's breathing zone were also determined. The measurements of concentrations were made inthe summertime during a morning shift. To determine endotoxins concentration, the Chromogenic LimulusAmebocyte Lysate (LAL) Test was applied. The questionnaire data and determination results were subjectto a statistical analysis. No statistically significant relationship was found between the reported healthcomplaints and such variables as job title, exposure to endotoxins and glucans, tobacco smoking, ageand period of employment as sewage worker. The findings revealed that among the complaints, muscle andjoint ache was reported most frequently, while among the symptom clusters, the flu-like symptoms prevailed.These symptom clusters occurred most frequently in OC workers, and were least often found in SST workers.In the worker's breathing zone, the geometric mean concentration of endotoxins amounted to 20.3 ng/m3and of glucans to 7.76 ng/m3, and was not related to job title or job characteristics. A high correlationwas found between endotoxins and (1 --> 3)- beta -D-glucans concentrations (Pearson correlation coefficient0.86, p < 0.0005).