We carried out spectrophotometrically calibrated imagery of NGC4736, with narrow band interference filters in emission lines and continua with high S/N ratio.
We present a catalogue of 90 HII regions with positions,
sizes, emission line intensities and adjacent continua
fluxes of [OII]
, H
, [OIII]
, H
,
[SII]
, and [SIII]
lines.
They are mainly distributed in a ring of 
in diameter.
There is no HII region comparable to 30 DOR
in this galaxy, since the mean H luminosity is 
.
The HII regions size distribution presents a characteristic
diameter 
and follows the relation 
.
The physical properties of the set of HII regions are:
; temperatures of ionizing sources are in the
range 
K;
masses of the ionizing clusters are in the range 
.
HII regions ionizing associations in NGC4736 can reach masses
up to 
.
There are indications that the most massive ionizing associations,
produce enough supernovae and/or massive star winds, as to fade out
the ionizing gas, transforming the HII regions in an optically thin one.
The radial surface brightness distribution of the galaxy
is better fitted by the superposition of a de
Vaucouleurs', a thin and a thick exponential disk laws.
This configuration was also found in NGC5383.
It was put in evidence an oval ring of 
, elongated in
the same direction as the small central bar.
The monochromatic colors show that oustside the ring of HII regions, the disk presents a contribution of a younger stellar population than that in its inner part.
Acknowledgements
We thank Dr. E. Bica for making available his templates of stellar population and Dr. R. Cid-Fernandes who provided the "ET" code. The Jacobus Kapteyn Telescope is operated on the island of La Palma by the Royal Greenwich Observatory in the Spanish Observatorio del Roque de Los Muchachos of the Instituto de Astrofı sica de Canárias. This project was partially supported by the spanish Dirección General de Investigación Cientı fica y Técnica, grant n PB94-0433. This work was also partially supported by the brazilian institutions CNPq and FINEP.