I have been asked to write a foreword to the next edition of the Vademecum of Clinical Bio­ chemistry renamed to Differential Diagnosis by Laboratory Medicine. The Editor in-Chief, Professor Dusan Mesko, conceived the idea of the Vademecum during a very intensely, intellectually active period as a visiting Olga Havel Fellow from Slovak Republic at the Mayo Clinic in Rochester. It was here during his study stay that much of the conceptual planning and detailed realization was being completed. It was with much interest that I observed Professor Mesko in his effort, and I know while here he has gained admiration of those who had the privilege of interacting with him. When the first edition of the Vademecum ap­ peared and we received the copy for the Mayo Library and for myself, I was overcome with a genuine sense of joy. In this era of rapid information and the need to access usable information book such as this cannot be but judged extremely useful. It is my hope that this work, which attests to the thoroughness of Professor Mesko's and his co-workers efforts will prove to be fruitful for the students quick reference, for clinicans and house officers lightening of burdens, particularly of on-call nights, and for the teaching staff as well to quickly access needed information. With these sentiments, we wish the authors and the book well and also hope that the potential widening circle of readers and users will benefit from the work presented.