Dry powder inhalers and methods are provided that facilitate deagglomeration of powdered medicament during inspiration. A dry powder inhaler includes a dry powder medicament container assembly, and an elongated dry powder delivery tube having an inlet at one end that communicates with a dose container, and an outlet or inhalation port that extends from the inhaler housing at an opposite end. The delivery tube includes one or more apertures adjacent the inlet that cause cyclonic or turbulent airflow through the delivery tube. The inner surface of the delivery tube has a polygonal configuration and the cyclonic air stream bounces off the polygonal inner surface numerous times as the air stream flows through the delivery tube. Another dry powder inhaler includes a deagglomeration chamber with a polygonal inner surface. An air stream containing dry powder medicament is directed into the deagglomeration chamber and impacts the polygonal inner surface numerous times.