Wall Street analysts polled by Reuters had forecast a 0.4 percent rise in inventories compared with a revised 0.5 percent increase in March. This had initially been reported as up 0.4 percent.
Economists see rising inventories either as a sign of confidence in future demand, or as a result of an unexpected decline in sales which has led to involuntary stock building.
Deciding which of these interpretations is the case is helped by a sense of whether stocks are lean by historical standards from looking at the sales-to-inventories ratio.
This measure of the number of months it would take to deplete stocks at the current rate of sales declined a touch to 1.30 months from 1.31 months in March, matching the record low first hit last year.
At a more detailed level within the report, retail inventories (search) rose 0.2 percent in April while retail sales advanced 1.5 percent.
Inventories at motor vehicle and parts dealers were up 0.2 percent, sales rose 2.0 percent and the motor sales-to-inventories ratio was almost unchanged at 2.0 months. The Commerce Department said last week that wholesale inventories climbed 0.8 percent in April as auto stocks swelled.