Background: Most errors in the venous blood testing process are preanalytical, i.e. they occur before the sample reaches the laboratory. Unlike the laboratory analysis, the preanalytical phase involves several error-prone manual tasks not easily avoided with technological solutions. Despite the importance of the preanalytical phase for a correct test result, little is known about how blood samples are collected in hospitals. Aim: The aim of this thesis was to survey preanalytical procedures in hospitals to identify sources of error. Methods: The first part of this thesis was a questionnaire survey. After a pilot study (Paper I), a questionnaire addressing clinical chemistry testing was completed by venous blood sampling staff (n=314, response rate 94%) in hospital wards and hospital laboratories (Papers II–IV). The second part of this thesis was an experimental study. Haematology, coagulation, platelet function and global coagulation parameters were compared between pneumatic tube-transported samples and samples that had not been transported (Paper V). Results: The results of the questionnaire survey indicate that the desirable procedure for the collection and handling of venous blood samples were not always followed in the wards (Papers II–III). For example, as few as 2.4% of the ward staff reported to always label the test tube immediately before sample collection. Only 22% of the ward staff reported to always use wristbands for patient identification, while 18% reported to always use online laboratory manuals, the only source of updated information. However, a substantial part of the ward staff showed considerable interest in re-education (45%) and willingness to improve routines (44%) for venous blood sampling. Compared to the ward staff, the laboratory staff reported significantly higher proportions of desirable practices regarding test request management, test tube labelling, test information search procedures, and the collection and handling of venous blood samples, but not regarding patient identification. Of the ward staff, only 5.5% had ever filed an error report regarding venous blood sampling, compared to 28% of the laboratory staff (Paper IV). In the experimental study (Paper V), no significant preanalytical effect of pneumatic tube transport was found for most haematology, coagulation and platelet function parameters. However, time-to-clot formation was significantly shorter (16%) in the pneumatic tube-transported samples, indicating an in vitro activation of global coagulation. Conclusions. The questionnaire study of the rated experiences of venous blood sampling ward staff is the first of its kind to survey manual tasks in the preanalytical phase. The results suggest a clinically important risk of preanalytical errors in the surveyed wards. Computerised test request management will eliminate some, but not all, of the identified risks. The better performance reported by the laboratory staff may reflect successful quality improvement initiatives in the laboratories. The current error reporting system needs to be functionally implemented. The experimental study indicates that pneumatic tube transport does not introduce preanalytical errors for regular tests, but manual transport is recommended for analysis with thromboelastographic technique. This thesis underscores the importance of quality improvement in the preanalytical phase of venous blood testing in hospitals.