The suite of etchings called by Piranesi the Grotteschi, published in 1750 in the compilation volume Opere Varie, have for more than two-hundred and fifty years eluded interpretation. Long recognised by scholars as being 'touched by the artist's tragic imagination', more recent 'attempts to reduce the Grotteschi collectively or individually, to a specific, hermetic philosophical system have met with little success' In this volume these four magnificent prints are viewed as pivotal works in Piranesi's early output and a comprehensive narrative interpretation of their meaning is proposed adopting an approach, analogous to that applied by Wilton- Ely to explain the iconography of the Piazza dei Cavalieri di Malta, or that used by Gavuzzo-Stewart in her clear penetration of the Carceri. This study which follows step-by-step Piranesi's youthful artistic and intellectual endeavours between the Venice of Scalfarotto and Tiepolo and the Rome of Gian Battista Nolli, Giovanni Gaetano Bottari and the enlightened Corsini court proposes the Grotteschi as both testament and culmination of his first decade's experiences. For Piranesi the years upto1750 were particularly fecund: they are marked by apprenticeships in Venice and Rome, by economic difficulties, by successes and failures, and incessant travels in search of vocational fulfilment. In following these important years we are able to trace how they contribute to Piranesi's rapid intellectual development and to his evolution of an original, vital, graphic idiom that finds its first mature expression in the Grotteschi universally recognised as the artist's most 'venetian' works. Considered through the viewing filter of the paragone the Grotteschi are presented as Piranesi's expression of direct rivalry with the great etching masters of the past: from Mantegna, Durer and Rembrandt to Salvator Rosa, Castiglione, della Bella and Tiepolo, as well as his bid to establish his own place among their revered ranks. These works also represent the culmination and conclusion of a series of experiments, protracted over the course of a decade, in which Piranesi appears to have attempted to develop the picturesque capriccio of ruins into a type of image capable of bearing specific meaning, thereby giving visual form to his idea of 'ruine parlanti'. In conclusion, following a close reading of the visual and textual sources that inform Piranesi's Grotteschi, the impact of these etchings is assessed on the artist's work of the 1760s, in particular on his only built edifice, the church of the Knights of Malta, Santa Maria del Priorato, which is the culmination of a second phase of intense creativity in the artist's career.