We introduce a data structure that allows for efficient (probabilistic) presence proofs and non-probabilistic absence proofs in a bandwidth efficient and secure way. The Bloom tree combines the idea of Bloom filters with that of Merkle trees. Bloom filters are used to verify the presence, or absence of elements in a set. In the case of the Bloom tree, we are interested to verify and transmit the presence, or absence of an element in a secure and bandwidth efficient way to another party. Instead of sending the whole Bloom filter to check for the presence, or absence of an element, the Bloom tree achieves efficient verification by using a compact Merkle multiproof.