OBJECTIVE: Determine serum lipid and general health/fitness alterations following a 5-month wildfire suppression season. METHODS: We recruited 100 wildland firefighters (WLFFs) to a 5-month pre- to post-season observational study. Nude body mass, blood pressure (BP), grip strength, and steptest heart rate (HR) were recorded. Blood samples were collected for lipid panel analysis (total cholesterol, high density lipoproteins (HDL)-cholesterol, low density lipoproteins-cholesterol, very low density lipoproteinscholesterol, triglycerides, triglyceride:HDL-cholesterol ratio). Two-tailed dependent t tests determined statistical significance (P < 0.05). RESULTS: There were pre- to post-season changes in nude body mass (+2 ± 4%, P  = 0.001), systolic BP (-2 ± 10%, P  = 0.01), step-test HR (-5 ± 10%, P  < 0.001), and all serum lipids (total cholesterol: +5 ± 14%, P  = 0.02, HDL-cholesterol: = 1 ± 17%, P  = 0.04, low density lipoproteins-cholesterol: +8 ± 22%, P  = 0.02, very low density lipoproteins-cholesterol: +31 ± 49%, P  < 0.001, triglycerides: +30 ± 49%, P  < 0.001, triglyceride:HDL-cholesterol ratio: +37 ± 58%, P  < 0.001). Pre- to post-season diastolic BP (P = 0.12) and grip strength (P = 0.60) remained stable. CONCLUSIONS: WLFFs demonstrate maladaptive serum lipids and body mass alterations despite subtle aerobic fitness improvements.