Hare, Donovan R.McCuaig, William2010-05-172010-05-1719912010-05-17http://hdl.handle.net/1828/2767It is shown that the vertex connectivity of the block-intersection graph of a balanced incomplete block design, BIBD(v,k,1), is equal to its minimum degree. A similar statement is proved for the edge connectivity of the block-intersection graph of a pairwise balanced design, PBD(v,k,1). A partial result on the vertex connectivity of these graphs is also given. Minimal vertex and edge cuts for the corresponding graphs are characterized.entechnical reports (mathematics and statistics)Technical ReportDepartment of Mathematics and Statistics