The Boyden chamber was designed over 40 years ago (1). It was first designed to study chemotaxis but later modifications resulted in it becom-ing one of the most popular tools for assessing cell motility and invasion. The classic Boyden chamber consists of two compartments separated by a filter membrane, which, with its micro-porous surface, provides a barrier so that cells cannot pass through except by active migration. For chemotaxis analysis, cells are seeded onto the upper compartment, and the chemoattractant is placed in the lower compartment. After incubation for a period less than the time taken for cells to divide, the degree of chemotactic response can be microscopically determined by count-ing the percentage of transmigrated cells compared to the original number of seeded cells (1). In order to adapt the Boyden chamber to other applications such as quantitating the invasive poten-tial of tumor cells, various extracellular matrix molecules can be coated onto the membrane. These coating materials can be laminin, collagen, natural basement membrane, or the most widely used substance known as Matrigel™ (BD Biosciences, San Jose, CA, USA; Ref-erences 2–5). The porous membrane is occluded by Matrigel, therefore mim-icking the extracellular environment. Only invasive cells that have digested the gel will reach the underside of the membrane.Currently, there are several com-mercial and in-house versions of the Boyden chamber in use (6–8). All chambers are square or rectangular in shape and can be made in either a single- or multi-well format. Apart from a few newly developed but rather expensive commercial products, most of the Boyden assay systems are time-consuming, technically demanding, and cumbersome. They are prone to common errors such as: (i) the Matrigel coating is often irregular or disrupted, resulting in uneven cell invasion; (ii) the pro-cess of removal of the inserts some-times leads to cross-contamination and variability in results; (iii) the recovery of transmigrated cells is notoriously difficult, especially for inexperienced users; and (iv) the manual fixing, cell staining, and cell counting further serve to amplify the inconsistency. As a consequence, many results of the Boyden cham-ber assays have been shown to vary significantly from one laboratory to another, and even within the same laboratory.To help circumvent some of these problems, here we describe a few simple but very effective modifica-tions to the Boyden chamber. Our intent is to provide researchers who wish to screen for anti-invasive or anti-metastatic agents a cheap yet accurate and reliable alternative. First, we have modified the typi-cal design of the Boyden chamber into a trapezoid mode (Figure 1A). Alteration of the top plate to 205 mm long and 95 mm wide enabled us to arrange a total of 24 experi-mental wells (12 mm in diameter per well) to provide a versatile appa-ratus (Figure 1, B and C).Of all the problems associated with the conventional assay, prob-ably the most critical one is the loss of cells when washing and recover-ing them for further analyses. This problem is mainly due to the fact that the side-sampling ports are very narrow, causing difficulty in recovering transmi-grated cells, and the exhaust pipe is too short (i.e., 10–13 mm in length), which results in the overflow of cell popula-tions during washes and inaccurate cell counts. To solve these problems, we enlarged the bottom plate to 205 mm long and 135 mm wide to make the whole chamber appear as a trapezoid.