CONDITIONAL (turbulent) isodensity contours and cross sections of the joint probability density functions of the axial («) and radial (v) velocity fluctuations, and temperature fluctuation (0) are obtained in a slightly heated round jet with a coflowing external stream. Also obtained are the occupancy times in various quadrants and the quadrant contributions to average fluxes (uv}> , and {vB}. Comparison with corresponding quantities of the appropriate bivariate Gaussian density functions shows that departures from Gaussianity are less pronounced for the outward radial motion than for the inward radial motion associated with the possibly newly entrained fluid. Contents Previous measurements1'2 in axisymmetric jets have shown that turbulent fluctuations are closely Gaussian near the axis but become increasingly non-Gaussian in the intermittent region. Although fluctuations in the turbulent region only of the flow (designated below as conditional quantities) are known to be more closely Gaussian than the conventional fluctuations, significant departures from Gaussian flow persist.3 The objective of this paper is to explore these departures in some detail in the case of a slightly heated axisymmetric jet with a coflowing external stream, and to relate these departures to the physical processes occurring in the flow. The jet velocity at the exit of the nozzle (diameter = 2 cm) was 32 ms ~ ], and that of the coflowing stream was 4.8 ms ~ l. All measurements were made at a streamwise station 59 diameters downstream of the nozzle exit. Velocity fluctuations were measured with an X wire, and temperature fluctuation was measured with a cold wire (l-/zm diameter operated at 0.1 mA) located at about 1 mm from the midpoint of the X wire. Further details on experimental conditions and signal processing can be found in Ref. 3. Isodensity contours of the joint density functions of pairs of fluctuations (ut, vt), (v {, 0,), and (ut, 0,) were obtained from measured joint density functions; here, suffix t indicates conditional quantities with respect to their own means. They were then compared with the corresponding isodensity contours of the vibariate Gaussian density function. Conditional averages ut, vt, and 0, were also obtained according to relations similar to