Abstract: A fertility analyzer includes a laser beam impinging on a sperm sample in a capiliary, a first optical system including at least a first lens focusing the laser beam in the sample, and a second optical system including at least a second lens, a first diaphragm determining the volume element of the sample to be monitored, a second diaphragm determining the space angle of scattered light and a light intensity detecter. A signal processing device stores the signals from the light detector during a predetermined time separately for beams outgoing from the sperm sample in at least two chosen directions and computes at least two features having relation to the fertility of the sperm sample. A separator included in the combination of the first and second optical systems sorts out a determinable small section of the beam outgoing from the sperm sample in a direction lying in a plane approximately parallel to a plane including the capillary.