Doubly excited autoionizing states of C4+ ions between the N = 2 and N = 3 C5+ thresholds are calculated by use of the method of complex-coordinate rotation. Hylleraas-type wave functions for states of L less than or equal to 1 and products of Slater-orbital type wave functions for states of L greater than or equal to 2 are employed. Resonance parameters (both resonance positions and total widths) are obtained for states with parities of (-1)(L) With 0 less than or equal to L less than or equal to 5, and for states with parities of(-1)(L+1) with 1 less than or equal to L less than or equal to 4.