New orders, production and employment also improved, while inventories contracted for the ninth straight month.
"Supply chains are generally in balance," noted ISM Chairman Norbert Ore.
The organization's PMI (formerly known as the Purchasing Managers Index) registered 54.7 percent for April, up from 50.9 percent in March. A reading above 50 percent indicates that the manufacturing economy is expanding. A PMI in excess of 41.9 percent, over time, indicates expansion of the economy in general. The PMI average over the past 12 months has been 52.5 percent. The lowest reading was 49.3 percent in January.
ISM's New Orders Index was 58.5 percent in April, up from 51.6 percent in March. The Production Index was 57.3 percent, up from 53 percent. The Employment Index registered 53.1 percent versus 48.7 percent the previous month.
Manufacturers' inventories registered 46.3 percent compared to 47.5 percent the previous month. Supplier deliveries to manufacturers slowed for the 46th consecutive month. The Customers' Inventories Index was at 47 percent, one point lower than March. For the second consecutive month manufacturers indicated their customers' inventories were too low.
About half of survey respondents reported higher prices; only 4 percent reported lower prices. Ore said metals and energy are the areas of greatest concern to buyers. The complete report can be accessed at www.ism.ws.