The study of chemical abundance gradients can provide essential information on the evolution of disk galaxies. Here I briefly review our current observational knowledge concerning the abundances of the ionized gas (H ii regions and planetary nebulae) in nearby galaxies, and how they inform us about the time evolution of metallicity gradients.

I present an overview of the recent star formation activity in the outer disks of spiral galaxies, from the observational standpoint, with emphasis on the gas content, the star formation law, the metallicity and the stellar populations.

The spectroscopic study of blue supergiants in nearby galaxies can yield crucial information about the spatial distribution of extinction by dust, and can be successfully used to measure the metal content, abundance patterns, and distances of galaxies out to ~8 Mpc with current telescopes and instrumentation. We briefly review the results of an ongoing project in which the quantitative analysis of B- and A-type supergiants is used to independently test widely used metallicity diagnostics for star-forming galaxies and derive reddening-free extragalactic distances.

Spectrophotometric data of a number of planetary nebulae and compact HII regions of NGC 300 have been obtained with the FORS 2 spectrograph of the VLT. We present a preliminary analysis of such data.

We have obtained new spectrophotometric data for 28 Hii regions in the spiral galaxy NGC 300, a member of the nearby Sculptor Group. The detection of several auroral lines has allowed us to measure electron temperatures and direct chemical abundances for the whole sample. We determine for the first time in this galaxy a radial gas-phase oxygen abundance gradient based solely on auroral lines. The gradient corresponds to −0.077±0.006 dex kpc−1, which agrees very well with the galactocentric trend in metallicity obtained for 29 B and A supergiants in the same galaxy. The intercept of the regression for the nebular data virtually coincides with the intercept obtained from the stellar data. This result provides increased confidence on the direct method to determine extragalactic nebular abundances.

A supergiants are objects in transition from the blue to the red (and vice versa) in the uppermost HRD. They are the intrinsically brightest “normal” stars at visual light with absolute visual magnitudes up to −9. They are ideal to study young stellar populations in galaxies beyond the Local Group to determine chemical composition and evolution, interstellar extinction, reddening laws and distances. We discuss most recent results on the quantitative spectral analysis of such objects in galaxies beyond the Local Group based on medium and low resolution spectra obtained with the ESO VLT and Keck. We describe the analysis method including the determination of metallicity and metallicity gradients. A new method to measure accurate extragalactic distances based on the stellar gravities and effective temperatures is presented, the flux weighted gravity – luminosity relationship (FGLR). The FGLR is a purely spectroscopic method, which overcomes the uncertainties introduced by interstellar extinction and variations of metallicity, which plague all photometric stellar distance determination methods. We discuss the perspectives of future work using the giant ground-based telescopes of the next generation such as the TMT, the GMT and the E-ELT.

Many of the properties of massive stars in external galaxies, such as chemical compositions, mass functions, and ionizing fluxes, can be derived from the study of the associated clouds of ionized gas. Moreover, the signatures of Wolf-Rayet stars are often detected in the spectra of extragalactic H ii regions. This paper reviews some aspects of the recent work on the massive star content of nearby spiral galaxies, as inferred from the analysis of giant H ii regions. Particular attention is given to regions of high metallicity, including nuclear hot spots, and to the chemical abundance comparison between supergiant stars and ionized gas.

We report on the recent developments of our long-term investigation of the near-IR luminosity-metallicity relation for dwarf irregular galaxies in nearby groups. A very well-defined relation is emerging from our observational database, and a preliminary discussion of its implications is given.

We have carried out the wind analysis of six A-type supergiants in NGC 300. The derived Wind Momentum-Luminosity Relationship is compared with that of Galactic and M 31 blue supergiants and with theoretical models.

We review what is known about the large-scale trends in the sizes, luminosities, and mass functions of young stellar associations and clusters in nearby galaxies. We also describe an ongoing survey of massive young cluster populations in nearby galaxies.