Factory orders for U.S. manufactured goods rose 2.1 percent in the month to $485 billion after rising by 1.3 percent in April, a figure upwardly revised from a month earlier.
Fresh orders in May rose by $9.9 billion, the Census Bureau News said.
For May, transportation orders -- a category that includes big-ticket items, such as planes, trains and ships -- led the advance, rising 10.9 percent or by $7.3 billion to $74.5 billion.
Without transportation orders, factory orders, which were off a month earlier, rose by 0.6 percent, a sign that transportation orders are not carrying the entire increase.
Orders for durable goods in May, also up for three of the past four months, rose by $8.2 billion or 3.7 percent to $231.2 billion, the bureau said.
New orders for non-durable goods, which were down in April, rose by 0.7 percent or $1.8 billion to $253.8 billion.
Inventories of manufactured durable goods, up for four of the past five months, rose by 0.1 percent or $400 million to $377.7 billion, reaching the highest level since 1992.
Factories shipments also rose, climbing by $2.8 billion or 1.3 percent to $229.8 billion.