Alternating copolymerization of carbon monoxide with ethylene or 1-olefins in aqueous emulsion by water-insoluble palladium(II) complexes is reported. Latices of aliphatic polyketones (1-olefin/CO copolymers and ethylene/undec-10-enoic acid/CO terpolymers), prepared by catalytic polymerization, are described for the first time. An in situ catalyst system [{R2P(CH2)(3)PR2}Pd(OAc)(2)]/ strong acid (R = Ph or (CH2)(13)CH3) or well-defined complexes [{Ph2P(CH2)(3)PPh2}PdMe(NCCH3)]Y-+(-) = [B{3,5-(F3C)(2)C6H3}(4)](-) or SbF6-) were used in the form of a solution of the palladium(II) complex in miniemulsion droplets of a hydrocarbon dispersed in the continuous aqueous phase. Catalyst activities of up to 5 x 10(3) TO h(-1) slightly exceed those of nonaqueous polymerizations in methanol with the same catalysts. Polymer molecular weights (GPC vs PMMA standards) are typically M-w 2 x 10(5) (ethylene copolymers) respectively M-w 2 x 10(4) (1-olefin copolymers) with M-w/M-n 2-4. The 1-olefin copolymers exhibit glass transition temperatures of T-g = +10 to -55 degreesC, which is in the range desirable for latex applications.