_Tanagra lauta lauta_ Bangs and Penard: Thick-billed Euphonia.--According to Paynter (1955a:272), the only breeding record previously available is that of a male having slightly enlarged testes on February 12. Males taken on July 15 and on August 14 had fully enlarged testes; the gonads of several other specimens were apparently regressing, two specimens had begun to molt, and juveniles were molting into first winter plumage. Specimens (9): [Male], 40874, testis 7 × 4 mm. (July 15), and [Female], 40875, ova to 1 mm. (July 15), 7-1/2 km. W Escárcega; [Male], 40869, testis 6 × 4 mm., 14.5 gm. (August 14), [Male], 40870, testis 2 mm., 14.5 gm., molting--5th primaries ensheathed (August 14), [Male], 40867, imm., 12.6 gm. (August 14), [Female], 40868, imm., 14.4 gm. (August 14), [Male], 40871, testis 2 mm., 14.4 gm., molting--2nd, 3rd, and 4th primaries ensheathed (August 14), [Female], 40872, ovary granular, 7.8 gm. (August 14), and [Female], 40873, ovary granular, 13.0 gm. (August 15), all taken 4 km. NNE Felipe Carrillo Puerto. _Thraupis abbas_ (Deppe): Yellow-winged Tanager.--Paynter (1955a:273) reported breeding in this species in late April and late June. Gonads in our specimens were moderately active. Specimens (2): [Male], 40877, testis 6 × 4 mm., 43.0 gm., molting--1st and 2nd primaries ensheathed (July 15), 1 km. N, 13 km. W Escárcega; [Female] 40876, ovary 7 × 4 mm., (ova to 1 mm.), 42.1 gm. (July 29), Pueblo Nuevo X-can. _Spindalis zena benedicti_ Ridgway: Stripe-headed Tanager.--Two males in advanced molt but with enlarged gonads were taken on August 9 and 10 and seem to be the first records indicating breeding in this species on Isla Cozumel. Specimens (3): [Male], 40878, testis 9 × 7 mm., 32 gm., molting--5th primaries and middle pair of rectrices ensheathed (August 9), [Male], 40880, testis 5 × 3 mm., 30.0 gm., molting--3rd, 4th, 5th primaries and middle two pairs of restrices ensheathed (August 10), and [Female], 40879, ovary inactive, 28.1 gm., molting--remiges are new; secondary coverts ensheathed (August 10), 3-1/2 km. N San Miguel, Isla Cozumel. _Piranga roseogularis_ (Cabot): Rose-throated Tanager.--Breeding has been previously recorded from March 17 through May 11 (Paynter, 1955a:276). Our only specimen, a male in advanced molt, had enlarged (regressing) testes. Specimen (1): [Male], 40881, testis 7 × 5 mm., 24.2 gm., molting--4th and 5th primaries ensheathed (August 15), 4 km. NNE Felipe Carrillo Puerto.