This paper explores the relationship between infectious and non-infectious herd factors with the occurrence of pneumonia at slaughter and productive parameters in fattening pigs on 39 fattening herds. A questionnaire was used to obtain environmental and management factors (non-infectious factors). Blood samples and lungs were obtained from 35 pigs in each herd at slaughter. Serological testing was performed for antibodies against three respiratory pathogens (infectious factors): porcine reproductive and respiratory syndrome virus (PRRSV), Mycoplasma hyopneumoniae (Mh) and Aujeszky's disease Virus-gE protein (ADV-gE). Lung lesion classifications were catarrhal-purulent bronchopneumonia (CPBP), pleuropneumonia (PLP) and pleuritis. A mean lesion value (MLV) was calculated for each lesion. ANOVA and logistic regression assessed statistical associations among MLV, average daily gain (ADG) and feed conversion ratio (FCR) (dependent variables) with infectious and non-infectious factors (independent variables). Mh vaccination was associated with a significant decrease in CPBP; high Mh seroprevalences was associated with an increased level of CPBP. FCR was negatively related with high seroprevalences for ADV-gE and Mh. No significant associations were seen for ADG.