The decays of eta(c) to K(+)K(-)2(pi(+)pi(-)) and 3(pi(+)pi(-)) are observed for the first time using a sample of 5.8 x 10(7) J/psi events collected by the BESII detector. The product branching fractions are determined to be B(J/psi -> gamma eta(c)). B(eta(c) -> K+K-pi(+)pi(-)pi(+)pi(-)) = (1.21 +/- 0.32 +/- 0.24) x 10(-4), B(J/psi -> gamma eta(c)). B(eta(c) -> K*K-0*(0)pi(+)pi(-)) = (1.91 +/- 0.64 +/- 0.48) x 10(-4), and B(J/psi -> gamma eta(c)). B(eta(c) -> pi(+)pi(-)pi(+)pi(-)pi(+)pi(-)) = (2.59 +/- 0.32 +/- 0.47) x 10(-4). The upper limit for eta(c) -> phi pi(+)pi(-)pi(+)pi(-) is also obta...
