Microbial growth in fluid milk is one of the primary drivers of consumer liking. In an age of declining fluid milk consumption, control of microbial growth is critical. The 2 primary mechanisms of microbial spoilage in fluid milk are (1) post-pasteurization contamination (PPC) in the processing facility with psychrotolerant gram-negative bacteria (i.e., Pseudomonas); and (2) entry of psychrotolerant sporeforming bacteria (i.e., Paenibacillus) via raw milk contamination. Historically, the majority of fluid milk was spoiled by psychrotolerant gram-negative bacteria introduced into the product post-pasteurization. This type of contamination leads to drastically reduced shelf-life and significant flavor, body and odor defects. Results of recent work indicate that over 50% of fluid milk samples show signs of PPC, and of those samples, only 40% are contaminated with coliform bacteria, a commonly used indicator of PPC. These results indicate that PPC is still an issue that needs to be addressed by the dairy industry to offer consumers the highest quality fluid milk. Additionally, traditionally used hygiene indicators (i.e., coliform) need to be reexamined to provide relevant, actionable information to dairy processors regarding PPC. In the absence of PPC, psychrotolerant sporeforming bacteria become the limiting biological factor in fluid milk shelf-life. Addressing fluid milk spoilage from psychrotolerant sporeforming bacteria includes understanding and reducing the transmission of these organisms through identification of key management practices associated with their presence in raw milk, as well as sources of these organisms in the farm environment. Recent work indicates that udder hygiene and farm size are associated with the presence of psychrotolerant spores in raw bulk tank milk. Further, these organisms have been identified in diverse environmental samples (e.g., bedding, feed, manure and soil), indicating their abundance in the dairy farm environment. Ultimately, providing consumers with high quality, long lasting fluid milk requires a systems approach to preventing contamination of fluid milk throughout the grass to glass continuum.