ABSTRACT. The trunk of a knot in S 3 , defined by Makoto Ozawa, is a measure of geometric complexity similar to the bridge number or width of a knot. We prove that for any two knots K 1 and K 2 , we have tr(K 1 #K 2 ) = max{tr(K 1 ),tr(K 2 )}, confirming a conjecture of Ozawa. Another conjecture of Ozawa asserts that any width-minimizing embedding of a knot K also minimizes the trunk of K. We produce several families of probable counterexamples to this conjecture.