The present paper deals with tso-ch'an through a twofold approach, firstly by tracing back its historical roots, and secondly by describing the actual practice. Textual evidence demonstrates that the Chinese term tso-ch'an came into use centuries before the Ch'an School itself emerged serving as a technical term in both translated scriptures and indigeneous Chinese treatises on meditation. This brief excursion into the history of early Chinese Buddhism is followed by the clarification of the relationship between dhyāna (ch'an) and samādhi. Their Indian roots are clearly pointed out. The paper then proceeds to an analysis of the dvelopment of tso-ch'an in the context of Chinese Buddhism, Primarily the period of the first Ch'an Patriarchs. It is shown that since Bodhidharma, the Indian monk who was to be celebrated as the First Ch'an Patriarch in China, the masters in this line of transmission practiced ch'an in order to develop wisdom without going through the intermediate stage of samādhi. Besides Bodhidharma, the Fourth Patriarch Tao-hsin, the Fifth Patriarch Hung-jen, and the Sixth Patriarch Hui-neng are introduced. Their individual practices-and occasionally their writings-are discussed and respective background information is given in order to elucidate the conceptual changes that took place. In the case of Huineng, for example, sitting (tso) was not only not taken as necessary, but as a potential obstacle. The second part of the presest paper is devoted to the practical aspect of tso-ch'an. The three stages of regulating one's body, breath, and mind are dealt with in detail. General instructions conclude this exhaustive description, and a number of anecdotes illustrate certain misapprehension about practice before the author sets out to explain tso-ch'an as understood by the Ch'an School. In this context, the principles of both Silent Illumination Ch'an and Kung-an Ch'an are Presented by way of a wealth of historical stories. A note on the practice of tso-ch'an after enlightenment concludes the paper.