本文利用環保署和主計處合併的廠商資料來探討政府環境管制中稽查行動及民間非正式管制和廠商空污排放量之關係。在計量方法上，我們將稽查行動視為是一項內生變數，利用聯立模型同時分析政府稽查行動與廠商污染排放之決定。透過臺灣五個製造產業的實證結果發現，環保當局稽查行動的增加可降低廠商的污染排放，而環保當局也經常鎖定排放量較高的廠商為稽查對象。此外，規模較大、能源密集度較高和生產力較低的廠商，則有較高的空污排放量。擁有外資股權和從事外銷的廠商則較注重環保。本文並支持非正式管制對污染排放的抑制效果，在所得水準較高的縣市，廠商的污染排放量明顯下降。在稽查行動的決定因素方面，環保當局對於規模較大，設廠時間較早和雇用當地員工份額較高廠商，會投入較多的執法資源，平均環保職工人數較多的地區，廠商受到稽查的次數較高；而在工廠家數較少的縣市，廠商遭到稽核的機率則明顯降低。

　　　　　This article combines plant data from the Directorate General of Budget Accounting and Statistics (DGBAS) and air pollution data from the Environmental Protection Administration (EPA) to investigate the relationship between formal and informal regulations and air pollution emissions. We treat inspection as an endogenous variable and use a mixed model to examine the inspection and pollution regressions simultaneously. Using plant-level data from five Taiwanese manufacturing industries, we find that the EPA inspections significantly reduce air pollution emissions. The regulators usually target plants with a higher level of pollution emissions. Large-scale, energy-intensive, and less-productive plants have higher level of pollution emissions. In contrast, foreign-owned and export-oriented plants are cleaner than local counterparts and domestic-market-oriented plants. Our results also support the informal regulation hypothesis that local income is negatively associated with the pollution emissions. Regulators are more likely to inspect younger plants of large-scale and plants with a large local employment share.