This study had three aims. The first was to examine the influence of legislative and educational factors on facilities and equipment in dental practices, the second to find out if these and practice size affected standards and the third to assess the degree to which technique and other faults not connected with processing accounted for inadequate diagnostic quality in intra-oral radiography. Dentists from 62 practices returned questionnaires about the sizes of their practices, facilities and equipment for radiography and relevant updating, training and education of their staff. The quality of 305 radiographs taken in a sample of 11 practices was assessed. Ten examples of good radiographic practice were used to evaluate standards in the general practices. The 'good practice score' ranged from 2 (two practices) to 10 (one practice) with a mean of 6.2. Practices whose principals had engaged in the recommended educational activities scored more highly than those that had not (P < 0.05), and the mean scores in practices of two or more dentists were higher than in single-handed (P < 0.05). Of the 305 radiographs, the dentists, without the use of criteria to assess them, rejected 13.8%; with criteria they rejected 39.3% (P < 0.05). The researcher rejected 63.9% (P < 0.05). All films were processed under controlled conditions and it is likely that reject rates would have been higher under normal processing conditions. It is concluded that the use of criteria to assess radiographs and acceptance of postgraduate opportunities, particularly by single-handed practitioners, would improve the conduct of radiography. Further improvements might be gained by orienting updating courses and materials towards behavioural change.