The test tube holder includes an elongated tubular member which supports a pivot member and receives a removable adapter member. The adapter member accommodates a test tube and can be interchanged with another adapter member that accommodates a different size test tube. Biasing springs are provided in the adapter member to hold the test tube therein. The biasing force of the biasing springs against the test tube is predetermined to permit easy insertion and removal of the test tube from the adapter member. The test tube holder which includes the adapter member can be joined to other similar test tube holders in a manner which permits relative pivoting and tilting of one test tube holder with respect to another test tube holder. The test tube holder further includes a detent arrangement for inseparably detenting the adapter member in the tubular member when a test tube is present in the tubular member. Removal of the test tube from the test tube holder enables the adapter member to be separated from the tubular member.