Among the twenty-one Sakha-Samhitas of the Rigveda, as mentioned by Patanjali, only seven Samhitas were known by name and among these too, only one Sakala-Samhita was available in printed form so far. Now with the publication of the present editon of the Ashvalayana-Samhita a complete picture of a new Sakha-Samhita will come to fore for the first time. In comparison to the Sakala-Samhita, the Ashvalayana-Samhita has 212 additional mantras among which some occur in the common suktas and others form 16 additional complete suktas. Among these additional suktas special mention may be made of Kapinjala-sukta (II.44), Lakshmi-sukta (V.88-89), Pavamana-sukta (IX.68), Hiranya-sukta (X.130), Medha-sukta (X.155) and Manasa-sukta (X.171). The book in two volumes presents the full text of the Ashvalayana Samhita of the Rigveda with padapatha, marked with proper accent marks. The additional mantras of the Ashvalayana Samhita followed by their translation in English and Hindi are also provided at the end of the Samhita text. In a detailed introduction of the text the learned editor has examined the existence of Sakha-Samhitas of the Rigveda as mentioned by the Puranas, Patanjali, Mahidasa and other authorities, scrutinising textual evidence in support of them. The focus is, however, on the Ashvalayana-Samhita, with a background on Acarya Ashvalayana and exploring the antiquity, treatment of accent and padapatha of the text by referring to various sources.