This paper presents new evidence of asymmetric pass-through, the notion that upward cost shocks are passed through faster than downward cost shocks, in U.S. gasoline prices. Much of the extant literature comes to seemingly contradictory conclusions about the existence of an asymmetry, though the differences may be due to different aggregation (both over time and geographic markets) and the use of different price series including crude oil, wholesale, and retail gasoline prices. I utilize a large and detailed dataset to determine where evidence of a pass-through asymmetry exists, and how it depends on the aggregation and price series chosen by the researcher. Using the standard error correction model, I find evidence of pass-through asymmetry in the response of daily and weekly retail prices to wholesale rack price changes, though the magnitude varies by geographic market. On average, retail prices rise more than four times as fast as they fall. Branded gasoline features significantly more asymmetry with respect to rack prices compared with unbranded gasoline. Over time, nation-wide asymmetry varies significantly from year to year peaking in 2005. Midwest cities, like Louisville and Minneapolis, feature more asymmetry compared with other parts of the country. F-tests broadly confirm the results and illustrate that data selection and aggregation, as well as model specification, can have important implications on the findings of asymmetric pass-through.