Icelandic voiced fricatives frequently reduce in connected speech. However, systematic investigations of the phenomenon from acoustic and articulatory perspectives are lacking. To further the understanding of this lenition process, we present electromagnetic articulography and acoustic data from four speakers concerning the intervocalic realization of the dental and velar fricatives. The results show that lenition is mostly gradient, but some speakers and places of articulation exhibit two distinct modes suggesting a categorical distinction. Moreover, in some tokens, the fricative constriction is absent from the articulatory trajectories. Finally, the relation between lenition and speech rate, style, and stress is also subject to speaker- and gesture-specific effects. We conclude by evaluating how our findings challenge the common assumptions, made in the literature, that lenition is a change in gestural target or a perceptually driven phenomenon.