We present a signalling model which ascribes real effects to nominal disturbances. The market structure is characterized by imperfect information about prices which in the absence of aggregate informational asymmetries grants individual sellers monopoly status as in Diamond (1971). In addition, agents must incur an arbitrarily small cost to become perfectly informed about an aggregate nominal shock. If a seller has incurred this cost, its buyers may costlessly infer its private aggregate information from its nominal price. The solution of this signalling game specifies a set of sellers which separate and another Which pools and thus exhibits price inertia. The aggregate price level lies below the separating and above the pooling price.