This paper discusses pharmaceutical Quality by Design (QbD) and its application in ensuring pharmaceutical quality. QbD is a systematic approach to pharmaceutical development that involves designing and developing formulations and manufacturing processes to ensure predefined product quality. Key elements of QbD include defining target product quality profiles, designing product and manufacturing processes, identifying critical quality attributes, process parameters, and sources of variability, and controlling manufacturing processes to produce consistent quality over time. The paper contrasts QbD with the evaluation of product quality by testing alone. The FDA has developed a question-based review (QbR) system for its chemistry, manufacturing, and controls (CMC) evaluation of abbreviated new drug applications (ANDAs). This system incorporates elements of QbD and recommends that ANDAs be submitted using the common technical document (CTD) and include a quality overall summary (QOS) that addresses all QbR questions. The main benefits of this QbR system are to assure product quality through design and performance-based specifications, facilitate continuous improvement and reduce CMC supplements, enhance the quality of CMC reviews through standardized review questions, and reduce CMC review time when applicants submit a QOS that addresses the QbR questions. The concept of QbD was mentioned in the ICH Q8 guidance, which states that “quality cannot be tested into products, i.e., quality should be built in by design.” This paper discusses the pharmaceutical quality by design and describes how it can be used to ensure pharmaceutical quality with emphasis on solid oral dosage forms of small molecules. Under the traditional quality by testing (QbT) system, product quality is ensured by testing raw materials, drug substance manufacturing, a fixed drug product manufacturing process, in-process material testing, and end product testing. However, this system has led to excessive testing, extensive in-process tests, and a rigid specification that prohibits the release of products that may have acceptable clinical performance. The traditional regulatory evaluation system treats all products equally without regard to the risk to the consumer, leading to an imbalance in review time and resources. The paper concludes that QbD can transform the CMC review of ANDAs into a science-based pharmaceutical quality assessment.This paper discusses pharmaceutical Quality by Design (QbD) and its application in ensuring pharmaceutical quality. QbD is a systematic approach to pharmaceutical development that involves designing and developing formulations and manufacturing processes to ensure predefined product quality. Key elements of QbD include defining target product quality profiles, designing product and manufacturing processes, identifying critical quality attributes, process parameters, and sources of variability, and controlling manufacturing processes to produce consistent quality over time. The paper contrasts QbD with the evaluation of product quality by testing alone. The FDA has developed a question-based review (QbR) system for its chemistry, manufacturing, and controls (CMC) evaluation of abbreviated new drug applications (ANDAs). This system incorporates elements of QbD and recommends that ANDAs be submitted using the common technical document (CTD) and include a quality overall summary (QOS) that addresses all QbR questions. The main benefits of this QbR system are to assure product quality through design and performance-based specifications, facilitate continuous improvement and reduce CMC supplements, enhance the quality of CMC reviews through standardized review questions, and reduce CMC review time when applicants submit a QOS that addresses the QbR questions. The concept of QbD was mentioned in the ICH Q8 guidance, which states that “quality cannot be tested into products, i.e., quality should be built in by design.” This paper discusses the pharmaceutical quality by design and describes how it can be used to ensure pharmaceutical quality with emphasis on solid oral dosage forms of small molecules. Under the traditional quality by testing (QbT) system, product quality is ensured by testing raw materials, drug substance manufacturing, a fixed drug product manufacturing process, in-process material testing, and end product testing. However, this system has led to excessive testing, extensive in-process tests, and a rigid specification that prohibits the release of products that may have acceptable clinical performance. The traditional regulatory evaluation system treats all products equally without regard to the risk to the consumer, leading to an imbalance in review time and resources. The paper concludes that QbD can transform the CMC review of ANDAs into a science-based pharmaceutical quality assessment.