A diagnostic test was used to assess the mathematical knowledge and skills in 545 experienced nurses and 197 student nurses. The main purpose of this study was to investigate if student nurses and registered nurses have adequate knowledge and skills in drug dosage calculation. Nine out of fourteen test items were solved accurately and no differences were found in the average performance between the two groups. To evaluate physicians' knowledge about statutory regulations on drug prescription and legal responsibility, 36 physicians from different health care areas answered a questionnaire. The answers revealed that the majority was not familiar with these regulations. The results are discussed in relation to nurse education and the physicians' legal responsibility in connection with drug administration and prescription.