Abstract: An automatic decapping device for test tubes is capable of decapping 20 or more test tubes pre-loaded onto a round carousel. A small motor drives three offset cams. The first offset cam pushes a decap/eject arm over the cap of a tube. The cam and associated drive arms and brackets move a needle down and into the cap. The decap arm and needle are then raised and pull the cap upward and back, removing the cap. An ejection lever then removes the cap from the needle and the cap is fed down a disposal chute. A second offset cam simultaneously moves a support arm onto the lower part of the vertical tube to support the tube as the decapping occurs. As the decap/eject and support arms return to their home positions a third offset cam drives the carousel to position the next tube in front of the decap/eject and support arms and the cycle begins again. A one-way spring ratchet positioning mechanism allows for the incremental positioning of each tube in proper position for each decapping cycle.