The properties of violent star formation regions in the arms of spiral galaxies are reviewed with the aim of providing the foundations on which models of nuclear starbursts can be built. It is argued that the classical examples of extranuclear starbursts, giant HII regions and Superassociations, are closely related but fundamentally different classes of objects; their properties are reviewed and discussed in detail.

It is shown that giant HII regions are a homogeneous class of gravitationally bound objects ionized by starburst clusters and that the initial mass functions of these clusters change according to their chemical composition being flatter for metal poor systems. Superassociations are loose associations of associations which generally contain one or more giant HII regions. Star formation in superassociations is self-sustaining and therefore these structures may last much longer than individual giant HII regions.

Isolated superassociations or HII galaxies are shown to have the same global properties as giant HII regions in late type galaxies. In particular, the correlations between Hβ luminosity and emission line velocity width are similar for both classes. Since HII galaxies can be observed out to large distances this correlation provides a potentially powerful method to calibrate the extragalactic distance scale. A preliminary calibration gives HO = 95 ± 9 km/sec/Mpc.

The relations between the properties of giant HII regions and Superassociations with those of their parent galaxies are briefly discussed.

This paper is aimed at providing a review of recent observational facts regarding blue compact galaxies. Tightening together flux measurements from the UV to the radio range now allow us to draw a somewhat improved, more self-consistent picture of these objects. Many questions are still open however, about their nature and evolution.

Kinematical and photometric studies of nests of interacting galaxies are described. Velocity fields of 22 nests were obtained using the 6-meter telescope of the Special Astronomical Observatory of Sciences Academy of USSR. UBV-photometry carried out with 125-cm telescope of Sternberg Institute has shown that the majority of nests is blue and undergoes intense star formation. Nests are found to be of different types:among them there are single SB and dwarf Irr galaxies with super-giant HII -regions as well as tight pairs and multiple systems of galaxies. Multiple systems classified as nests are shown to be dynamically stable.

The results of a spectral study of the galaxy Mr 297 with the 6-m telescope are presented. Estimations of mass and heavy element abundance for some knots in galaxy are made. Chemical composition of these knots is close to the normal one.

It was during the fifties that Academician Ambartsumian first raised the issue of the activity of nuclei of galaxies, long before the subject became fashionable. An elaboration on these ideas may be found for example in Ambartsumian's report to the 1970 Vatican meeting. The issues which he raised pertain to the physics of the nuclei and their interaction with the surrounding galaxy, and perhaps even beyond. In the meantime, a large body of data has become available and has been reported at this meeting, and it is clear that the activity of nuclei is of paramount importance, even though a common view on all aspects has not yet been achieved.