The BOILED-Egg model is a predictive tool for estimating gastrointestinal absorption and brain penetration of small molecules. It uses physicochemical properties such as lipophilicity (log P) and polarity (polar surface area, PSA) to predict these properties. The model is based on a two-dimensional plot of these descriptors, where the region of well-absorbed molecules forms an ellipse known as the Egan egg. This model has been refined to include brain penetration prediction, resulting in the BOILED-Egg model, which combines both gastrointestinal absorption and brain penetration predictions. The model was developed by curating human intestinal absorption (HIA) data and blood-brain barrier (BBB) permeation data. The HIA dataset included 660 small molecules, while the BBB dataset included 260 molecules. The model was validated using cross-validation and showed high accuracy in predicting absorption and brain penetration. The BOILED-Egg model has been shown to be effective in drug discovery, as demonstrated by its application in the development of drugs such as telaprevir and the optimization of BCR-ABL inhibitors and AMPA receptor modulators. The BOILED-Egg model provides a rapid, intuitive, and statistically robust method for predicting the passive gastrointestinal absorption and brain access of small molecules. It is a valuable tool for drug discovery and development, as it allows for the efficient screening of compounds and the optimization of their physicochemical properties to enhance their pharmacokinetic profiles. The model is supported by extensive data and has been validated through multiple studies, making it a reliable and practical tool for the pharmaceutical industry.The BOILED-Egg model is a predictive tool for estimating gastrointestinal absorption and brain penetration of small molecules. It uses physicochemical properties such as lipophilicity (log P) and polarity (polar surface area, PSA) to predict these properties. The model is based on a two-dimensional plot of these descriptors, where the region of well-absorbed molecules forms an ellipse known as the Egan egg. This model has been refined to include brain penetration prediction, resulting in the BOILED-Egg model, which combines both gastrointestinal absorption and brain penetration predictions. The model was developed by curating human intestinal absorption (HIA) data and blood-brain barrier (BBB) permeation data. The HIA dataset included 660 small molecules, while the BBB dataset included 260 molecules. The model was validated using cross-validation and showed high accuracy in predicting absorption and brain penetration. The BOILED-Egg model has been shown to be effective in drug discovery, as demonstrated by its application in the development of drugs such as telaprevir and the optimization of BCR-ABL inhibitors and AMPA receptor modulators. The BOILED-Egg model provides a rapid, intuitive, and statistically robust method for predicting the passive gastrointestinal absorption and brain access of small molecules. It is a valuable tool for drug discovery and development, as it allows for the efficient screening of compounds and the optimization of their physicochemical properties to enhance their pharmacokinetic profiles. The model is supported by extensive data and has been validated through multiple studies, making it a reliable and practical tool for the pharmaceutical industry.