Dynamic processes do play an important role in the pathogenesis of intramammary infections (IMI). However, the dynamics of IMI were not considered in previous models to estimate the economic impact of IMI. A bio-economic model that includes the dynamics of infection was developed to simulate IMI caused by Staphylococcus aureus, Streptococcus uberis, Streptococcus dysagalactiae, and Escherichia coli to estimate there economic impact in Dutch dairies. The model simulates 100 dairy cows in a quota situation for one year. The dynamics of IMI were incorporated based on a Reed-Frost model for S. aureus, S. uberis, and S. dysagalactiae IMI, and based on a Greenwood model for E. coli IMI. Economic analysis was conducted per pathogen for clinical and subclinical IMI; separately. The model was validated based on literature methods and deemed a credible and valid. The total annual net costs varied widely for S. aureus, clinical or subclinical IMI costs were 1497 (0-4867) and 1097 (0-3640) per herd; respectively. Most important factors contributing to the total net cost were culling and milk production loss. The total annual net cost increased exponentially with the increase in the transmission rate of infection and was highly sensitive in case of S. aureus IMI. The relationship seemed linear in case of E. coli IMI. The model is a good tool to incorporate IMI management to provide precise economic advices for decision making.