Ultrasound assistance is a growing trend in analytical chemistry. From the most basic use for cleaning to facilitating or making possible different steps of the analytical process - particularly those involved in sample preparation - ultrasonic devices are gaining the confidence of analytical chemists who use them for helping in steps ranging from sampling through to detection. In this first part of the article, we present an overview of the principles and the uses of these devices for improving, accelerating or automating sample preparation. We compare them with well-established alternatives and critically comment upon them. (C) 2004 Elsevier Ltd. All rights reserved.