Solubility, dissolution, and precipitation in the gastrointestinal tract can be critical for the oral bioavailability of weakly basic drugs. To understand the dissolution and precipitation during the transfer out of the stomach into the intestine, a multicompartment transfer system was developed by modifying a conventional dissolution system. This transfer system included gastric, intestinal, sink and supersaturation, and reservoir compartments. Simulated gastric fluid and fasted state simulated intestinal fluid were used in the gastric and intestinal compartment, respectively, to mimic fasted condition. The new transfer system was evaluated based on 2 model weak bases, dipyridamole and ketoconazole. Traditional 2-stage dissolution using 250 mL of simulated gastric fluid media, followed by 250 mL of fasted state simulated intestinal fluid, was used as a reference methodology to compare dissolution and precipitation results. An in silico model was built using R software suite to simulate the in vitro time-dependent dissolution and precipitation process when formulations were tested using the transfer system. The precipitation rate estimated from the in vitro data was then used as the input for absorption and pharmacokinetic predictions using GastroPlus. The resultant simulated plasma concentration profiles were generally in good agreement with the observed clinical data, supporting the translatability of the transfer system in vitro precipitation kinetics to in vivo. Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.