Inability to use inhalers effectively is known to adversely affect the delivery of drug. It is assumed that increasing competence to use inhalers will lead to improved drug delivery. However many subjects appear competent (are able to use a device effectively) but contrive to use the device in a sub-optimal way in routine use. This study aimed to explore levels of True device compliance, that is the extent to which devices are used effectively in routine use, and to explore the influences of age and device on this parameter. The ability of 53 asthmatic patients aged 1-88 years to use their corticosteroid inhaler was assessed by a single investigator. In addition information regarding patient behaviour in routine practice was explored in a structured interview. True device compliance was defined to occur when a subject was rated competent and did not report contrivance. Competence was related to device type. All subjects using a holding chamber [pMDI + HC] (N = 21) or breath activated inhaler (N = 5) could demonstrate an adequate technique compared with only 9 (47%) of those prescribed a pMDI. However only 4 (19%) prescribed a pMDI + HC were true device compliant with the majority regularly using the pMDI alone while (42%) of those prescribed a pMDI were True device compliant. Since 82% of patients over 65 were prescribed pMDI alone, and 92% of patients up to 5 years were prescribed pMDI + HC, True device compliance was low among both groups. Only 33% of patients over 65 prescribed pMDIs were able to use them competently. Lack of competence, particularly in the elderly, and contrivance, particularly common amongst those using holding chambers, are two important but independent impediments to effective inhaled therapy.