James Siena’s sprawling show of mostly new works and some older materials, filling PaceWildenstein’s hangar-like 22nd Street premises, is a landmark in the development of this artist. Mr. Siena has been known for highly wrought, invariably intimate, abstract works on paper or panel. His imagery entailed intensely concentrated geometric patterns executed freehand but adhering to strict mathematical rules.

His love of rules situated him firmly within a trajectory of modern American art, among such luminaries as Alfred Jensen (whose work Mr. Siena collects) and Sol LeWitt. Exuding the conceptualism of the latter and the funky faux-primitive decorative intensity of the former, Mr. Siena found himself the contemporary exemplar in a 40-year survey of rule-based art — which included Jensen and LeWitt — organized by Marc Glimcher three years ago.

But now this rule-fiend seems intent on breaking his own cardinal principles. His new work signals two points of departure with major implications for his practice. First, he is starting to work big, not simply in terms of larger surfaces but with scaled-up marks that suggest a freer, faster conception, and a determination to make a stronger initial impression than tended to be the case with the quirky, eccentric vocabulary of his previous work.

And second, this relentlessly abstract artist, whose style seems to fuse a myriad of ethnographic and art historical precedents, has started to admit the figure. This is in the form of grotesque faces, screaming or grimacing old men from German medieval art, arriving by way of Ivan Albright and Mad Max Magazine. There are also strange tantric-patterned decorations on erotic, onanistic themes. The genie is out of the bottle.

The experience in this richly diverse exhibition is not, however, of transition as much as consolidation: The new works, whether big loopy abstractions in fat confident brushstrokes or the weirdo figuration described above, seem legitimate outgrowths of the precious, tight, miniaturist Mr. Siena of old. And the old religion is still practiced: There are many gorgeously colored grids of comb motifs, for instance, dating from 2006 or 2007, hanging happily alongside the new genres.

The quality of line in the grotesques, meanwhile, relates to the quilt- or lattice-like grids and labyrinths of classic Siena pictures, not just formally but also in terms of their own morphology: The line seems as subservient to algorithm as depiction, even though they work depictively. In “First Old Man” (2006), for instance, there is more a sense that the figure emerged from a maze-like algorithm that went awry than that the eye-popping, snarling figure was himself the prime mover of the linear form meandering about the page. And yet this colon-like form, doubling back and forth on itself, perfectly describes the loose gums and folding flesh of a wrinkled geriatric.

The increased scale of Mr. Siena’s abstract paintings has opposite emotional implications to his figural drawings. Where the faces and bodies show a goofy, mortal, and thus vulnerable side of the artist’s personality, the large abstract works are cooler, somewhat more ethereal than his tighter, smaller ones. You sense the hand being more distant from the artist’s body in the bigger pieces, generally pages in portrait format at 60 by 40 inches, with cool, fluid results. In the intimate formats, where the aluminum or copper plates, or Masonite boards, are less than half that size, you feel the artist’s shoulders hunched over the support, the slim lines exacting a fiercer quality of concentration, more retinal, less muscular.

And yet, in part to contradict this observation while confirming it, one of the most glorious of his new, large-format linear abstractions, “Untitled (Brown White)” (2007), betrays a key aspect of his earlier miniaturist modus operandi: While the line follows a tight logic, it also fluctuates in color intensity in a way that suggests the mind deciding where to go next — the brush stops not just to ink but to think. A coiling thick line twists and turns to fill the whole page evenly, yet never overlaps itself, and rarely butts into itself.

Works in his new genres exude all the excitement of thematic departure, but the most intense pleasures in this show occur when Mr. Siena is on familiar ground — whether this is a result of this viewer’s comfort level or

the artist’s is a matter of conjecture. Unusually for an artist who is reported to be partially colorblind, Mr. Siena achieves exquisite, lyrical intensities of color relationship in his works in enamel on metal plates. “Heliopolis, third version” (2006) connotes the sun of its title with a close-knit gold and yellow shot through with dark blue. It is a tight composition in which the gaze is funneled into the center of the plate, while the inexactitude of this handmade image, with the pattern wobbling rather as if it were weaved than painted, reminds of the artifice and ensures a sense of flatness.

While Mr. Siena’s compulsive personal industry is taking his art in disparate directions simultaneously, it is reassuring to find him equally fascinated, and fascinating, in each of them.

Until April 26 (545 W. 22nd St., between Tenth and Eleventh avenues, 212-989-4258).