A review is presented of original multidimensional, intermediate-scale experiments involving NAPLs (nonaqueous phase liquids). The experimental approach at this scale can be viewed as an important intermediary between column studies and field trials. The primary advantage of intermediate-scale flow cell experiments is that field-scale processes can be simulated under controlled conditions. The experiments are frequently conducted to provide data sets to test and verify numerical and analytical flow and transport models. The controlled setting and laboratory instrumentation reduces the uncertainty in parameter estimation, allowing comparisons between simulation and experimental results to focus on flow and transport processes. A total of about 125 original contributions were identified and reviewed. Depending on the main topic of NAPL experimental research, the papers were divided into the following sections: (i) aqueous dissolution, (ii) enhanced remediation, (iii) flow behavior, (iv) quantification, and (v) imaging. In this review, the first two categories are discussed and suggestions for future research are provided. In a companion review, experimental work related to the other three categories is investigated. The aqueous dissolution category includes experiments in which pooled and entrapped NAPL removal occurs due to water flushing. The enhanced remediation section contains experimental contributions investigating surfactant flushing, alcohol flushing, surfactant and alcohol flushing combinations, dense brine strategies, hydraulic NAPL recovery, soil vapor extraction, air sparging, heat-based remediation, bioremediation, and other techniques.