This review paper discusses various in vitro methods for evaluating antimicrobial activity, emphasizing their advantages, limitations, and applications. The focus is on methods used to assess the antimicrobial properties of natural products, plant extracts, and microbial compounds. The paper highlights the importance of standardized testing methods in combating microbial resistance and improving the efficacy of antimicrobial agents. Common methods include agar disk-diffusion, antimicrobial gradient (Etest), agar well diffusion, agar plug diffusion, cross streak, and poisoned food methods. These methods are used to determine the minimum inhibitory concentration (MIC) and assess the bactericidal or bacteriostatic effects of antimicrobial agents. Additionally, thin-layer chromatography (TLC)-bioautography is described as a technique that combines TLC with biological detection to identify antimicrobial compounds. Dilution methods, such as broth and agar dilution, are also discussed, as they are essential for determining MIC values. The time-kill test is highlighted as a method to evaluate the dynamic interaction between antimicrobial agents and microorganisms, providing insights into the bactericidal or fungicidal effects. The ATP bioluminescence assay is described as a rapid and quantitative method for assessing microbial viability, while flow cytometry is noted for its ability to detect antimicrobial resistance and assess the impact of antimicrobial agents on microbial viability. The review emphasizes the need for standardized protocols in antimicrobial susceptibility testing, particularly for natural products, to ensure accurate and reproducible results. It also discusses the importance of proper inoculum preparation, growth medium, and incubation conditions in obtaining reliable data. The paper concludes that while many methods are available, standardization and careful application are crucial for effective antimicrobial testing and the discovery of new antimicrobial agents.This review paper discusses various in vitro methods for evaluating antimicrobial activity, emphasizing their advantages, limitations, and applications. The focus is on methods used to assess the antimicrobial properties of natural products, plant extracts, and microbial compounds. The paper highlights the importance of standardized testing methods in combating microbial resistance and improving the efficacy of antimicrobial agents. Common methods include agar disk-diffusion, antimicrobial gradient (Etest), agar well diffusion, agar plug diffusion, cross streak, and poisoned food methods. These methods are used to determine the minimum inhibitory concentration (MIC) and assess the bactericidal or bacteriostatic effects of antimicrobial agents. Additionally, thin-layer chromatography (TLC)-bioautography is described as a technique that combines TLC with biological detection to identify antimicrobial compounds. Dilution methods, such as broth and agar dilution, are also discussed, as they are essential for determining MIC values. The time-kill test is highlighted as a method to evaluate the dynamic interaction between antimicrobial agents and microorganisms, providing insights into the bactericidal or fungicidal effects. The ATP bioluminescence assay is described as a rapid and quantitative method for assessing microbial viability, while flow cytometry is noted for its ability to detect antimicrobial resistance and assess the impact of antimicrobial agents on microbial viability. The review emphasizes the need for standardized protocols in antimicrobial susceptibility testing, particularly for natural products, to ensure accurate and reproducible results. It also discusses the importance of proper inoculum preparation, growth medium, and incubation conditions in obtaining reliable data. The paper concludes that while many methods are available, standardization and careful application are crucial for effective antimicrobial testing and the discovery of new antimicrobial agents.