In this paper we propose a method to retrieve trademarks using query by sketches. The trademark images are first filtered to remove noise. Then each filtered image is segmented into regions based on pixel connectivity. For each region, a decision is made about whether thinning or edge extraction should be applied. Afterwards stroke tracing is performed to extract the sketch of the trademark. The user can then provide a query sketch that will be compared with those extracted sketches from the database trademark images in order to retrieve similar trademarks. Query by sketch is useful in the trademark retrieval application since the user can search for similar trademarks by providing a rough sketch instead of keywords. Our approach saves a lot of labor because it does not require the trademark database to be manually annotated with keywords and the experimental result shows that our scheme outperforms an existing method in terms of retrieval performance.